/*
* rculfhash.c
*
- * Userspace RCU library - Lock-Free Expandable RCU Hash Table
+ * Userspace RCU library - Lock-Free Resizable RCU Hash Table
*
* Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
+/*
+ * Based on the following articles:
+ * - Ori Shalev and Nir Shavit. Split-ordered lists: Lock-free
+ * extensible hash tables. J. ACM 53, 3 (May 2006), 379-405.
+ * - Michael, M. M. High performance dynamic lock-free hash tables
+ * and list-based sets. In Proceedings of the fourteenth annual ACM
+ * symposium on Parallel algorithms and architectures, ACM Press,
+ * (2002), 73-82.
+ *
+ * Some specificities of this Lock-Free Resizable RCU Hash Table
+ * implementation:
+ *
+ * - RCU read-side critical section allows readers to perform hash
+ * table lookups, as well as traversals, and use the returned objects
+ * safely by allowing memory reclaim to take place only after a grace
+ * period.
+ * - Add and remove operations are lock-free, and do not need to
+ * allocate memory. They need to be executed within RCU read-side
+ * critical section to ensure the objects they read are valid and to
+ * deal with the cmpxchg ABA problem.
+ * - add and add_unique operations are supported. add_unique checks if
+ * the node key already exists in the hash table. It ensures not to
+ * populate a duplicate key if the node key already exists in the hash
+ * table.
+ * - The resize operation executes concurrently with
+ * add/add_unique/add_replace/remove/lookup/traversal.
+ * - Hash table nodes are contained within a split-ordered list. This
+ * list is ordered by incrementing reversed-bits-hash value.
+ * - An index of bucket nodes is kept. These bucket nodes are the hash
+ * table "buckets". These buckets are internal nodes that allow to
+ * perform a fast hash lookup, similarly to a skip list. These
+ * buckets are chained together in the split-ordered list, which
+ * allows recursive expansion by inserting new buckets between the
+ * existing buckets. The split-ordered list allows adding new buckets
+ * between existing buckets as the table needs to grow.
+ * - The resize operation for small tables only allows expanding the
+ * hash table. It is triggered automatically by detecting long chains
+ * in the add operation.
+ * - The resize operation for larger tables (and available through an
+ * API) allows both expanding and shrinking the hash table.
+ * - Split-counters are used to keep track of the number of
+ * nodes within the hash table for automatic resize triggering.
+ * - Resize operation initiated by long chain detection is executed by a
+ * call_rcu thread, which keeps lock-freedom of add and remove.
+ * - Resize operations are protected by a mutex.
+ * - The removal operation is split in two parts: first, a "removed"
+ * flag is set in the next pointer within the node to remove. Then,
+ * a "garbage collection" is performed in the bucket containing the
+ * removed node (from the start of the bucket up to the removed node).
+ * All encountered nodes with "removed" flag set in their next
+ * pointers are removed from the linked-list. If the cmpxchg used for
+ * removal fails (due to concurrent garbage-collection or concurrent
+ * add), we retry from the beginning of the bucket. This ensures that
+ * the node with "removed" flag set is removed from the hash table
+ * (not visible to lookups anymore) before the RCU read-side critical
+ * section held across removal ends. Furthermore, this ensures that
+ * the node with "removed" flag set is removed from the linked-list
+ * before its memory is reclaimed. After setting the "removal" flag,
+ * only the thread which removal is the first to set the "removal
+ * owner" flag (with an xchg) into a node's next pointer is considered
+ * to have succeeded its removal (and thus owns the node to reclaim).
+ * Because we garbage-collect starting from an invariant node (the
+ * start-of-bucket bucket node) up to the "removed" node (or find a
+ * reverse-hash that is higher), we are sure that a successful
+ * traversal of the chain leads to a chain that is present in the
+ * linked-list (the start node is never removed) and that it does not
+ * contain the "removed" node anymore, even if concurrent delete/add
+ * operations are changing the structure of the list concurrently.
+ * - The add operations perform garbage collection of buckets if they
+ * encounter nodes with removed flag set in the bucket where they want
+ * to add their new node. This ensures lock-freedom of add operation by
+ * helping the remover unlink nodes from the list rather than to wait
+ * for it do to so.
+ * - There are three memory backends for the hash table buckets: the
+ * "order table", the "chunks", and the "mmap".
+ * - These bucket containers contain a compact version of the hash table
+ * nodes.
+ * - The RCU "order table":
+ * - has a first level table indexed by log2(hash index) which is
+ * copied and expanded by the resize operation. This order table
+ * allows finding the "bucket node" tables.
+ * - There is one bucket node table per hash index order. The size of
+ * each bucket node table is half the number of hashes contained in
+ * this order (except for order 0).
+ * - The RCU "chunks" is best suited for close interaction with a page
+ * allocator. It uses a linear array as index to "chunks" containing
+ * each the same number of buckets.
+ * - The RCU "mmap" memory backend uses a single memory map to hold
+ * all buckets.
+ * - synchronize_rcu is used to garbage-collect the old bucket node table.
+ *
+ * Ordering Guarantees:
+ *
+ * To discuss these guarantees, we first define "read" operation as any
+ * of the the basic cds_lfht_lookup, cds_lfht_next_duplicate,
+ * cds_lfht_first, cds_lfht_next operation, as well as
+ * cds_lfht_add_unique (failure).
+ *
+ * We define "read traversal" operation as any of the following
+ * group of operations
+ * - cds_lfht_lookup followed by iteration with cds_lfht_next_duplicate
+ * (and/or cds_lfht_next, although less common).
+ * - cds_lfht_add_unique (failure) followed by iteration with
+ * cds_lfht_next_duplicate (and/or cds_lfht_next, although less
+ * common).
+ * - cds_lfht_first followed iteration with cds_lfht_next (and/or
+ * cds_lfht_next_duplicate, although less common).
+ *
+ * We define "write" operations as any of cds_lfht_add, cds_lfht_replace,
+ * cds_lfht_add_unique (success), cds_lfht_add_replace, cds_lfht_del.
+ *
+ * When cds_lfht_add_unique succeeds (returns the node passed as
+ * parameter), it acts as a "write" operation. When cds_lfht_add_unique
+ * fails (returns a node different from the one passed as parameter), it
+ * acts as a "read" operation. A cds_lfht_add_unique failure is a
+ * cds_lfht_lookup "read" operation, therefore, any ordering guarantee
+ * referring to "lookup" imply any of "lookup" or cds_lfht_add_unique
+ * (failure).
+ *
+ * We define "prior" and "later" node as nodes observable by reads and
+ * read traversals respectively before and after a write or sequence of
+ * write operations.
+ *
+ * Hash-table operations are often cascaded, for example, the pointer
+ * returned by a cds_lfht_lookup() might be passed to a cds_lfht_next(),
+ * whose return value might in turn be passed to another hash-table
+ * operation. This entire cascaded series of operations must be enclosed
+ * by a pair of matching rcu_read_lock() and rcu_read_unlock()
+ * operations.
+ *
+ * The following ordering guarantees are offered by this hash table:
+ *
+ * A.1) "read" after "write": if there is ordering between a write and a
+ * later read, then the read is guaranteed to see the write or some
+ * later write.
+ * A.2) "read traversal" after "write": given that there is dependency
+ * ordering between reads in a "read traversal", if there is
+ * ordering between a write and the first read of the traversal,
+ * then the "read traversal" is guaranteed to see the write or
+ * some later write.
+ * B.1) "write" after "read": if there is ordering between a read and a
+ * later write, then the read will never see the write.
+ * B.2) "write" after "read traversal": given that there is dependency
+ * ordering between reads in a "read traversal", if there is
+ * ordering between the last read of the traversal and a later
+ * write, then the "read traversal" will never see the write.
+ * C) "write" while "read traversal": if a write occurs during a "read
+ * traversal", the traversal may, or may not, see the write.
+ * D.1) "write" after "write": if there is ordering between a write and
+ * a later write, then the later write is guaranteed to see the
+ * effects of the first write.
+ * D.2) Concurrent "write" pairs: The system will assign an arbitrary
+ * order to any pair of concurrent conflicting writes.
+ * Non-conflicting writes (for example, to different keys) are
+ * unordered.
+ * E) If a grace period separates a "del" or "replace" operation
+ * and a subsequent operation, then that subsequent operation is
+ * guaranteed not to see the removed item.
+ * F) Uniqueness guarantee: given a hash table that does not contain
+ * duplicate items for a given key, there will only be one item in
+ * the hash table after an arbitrary sequence of add_unique and/or
+ * add_replace operations. Note, however, that a pair of
+ * concurrent read operations might well access two different items
+ * with that key.
+ * G.1) If a pair of lookups for a given key are ordered (e.g. by a
+ * memory barrier), then the second lookup will return the same
+ * node as the previous lookup, or some later node.
+ * G.2) A "read traversal" that starts after the end of a prior "read
+ * traversal" (ordered by memory barriers) is guaranteed to see the
+ * same nodes as the previous traversal, or some later nodes.
+ * G.3) Concurrent "read" pairs: concurrent reads are unordered. For
+ * example, if a pair of reads to the same key run concurrently
+ * with an insertion of that same key, the reads remain unordered
+ * regardless of their return values. In other words, you cannot
+ * rely on the values returned by the reads to deduce ordering.
+ *
+ * Progress guarantees:
+ *
+ * * Reads are wait-free. These operations always move forward in the
+ * hash table linked list, and this list has no loop.
+ * * Writes are lock-free. Any retry loop performed by a write operation
+ * is triggered by progress made within another update operation.
+ *
+ * Bucket node tables:
+ *
+ * hash table hash table the last all bucket node tables
+ * order size bucket node 0 1 2 3 4 5 6(index)
+ * table size
+ * 0 1 1 1
+ * 1 2 1 1 1
+ * 2 4 2 1 1 2
+ * 3 8 4 1 1 2 4
+ * 4 16 8 1 1 2 4 8
+ * 5 32 16 1 1 2 4 8 16
+ * 6 64 32 1 1 2 4 8 16 32
+ *
+ * When growing/shrinking, we only focus on the last bucket node table
+ * which size is (!order ? 1 : (1 << (order -1))).
+ *
+ * Example for growing/shrinking:
+ * grow hash table from order 5 to 6: init the index=6 bucket node table
+ * shrink hash table from order 6 to 5: fini the index=6 bucket node table
+ *
+ * A bit of ascii art explanation:
+ *
+ * The order index is the off-by-one compared to the actual power of 2
+ * because we use index 0 to deal with the 0 special-case.
+ *
+ * This shows the nodes for a small table ordered by reversed bits:
+ *
+ * bits reverse
+ * 0 000 000
+ * 4 100 001
+ * 2 010 010
+ * 6 110 011
+ * 1 001 100
+ * 5 101 101
+ * 3 011 110
+ * 7 111 111
+ *
+ * This shows the nodes in order of non-reversed bits, linked by
+ * reversed-bit order.
+ *
+ * order bits reverse
+ * 0 0 000 000
+ * 1 | 1 001 100 <-
+ * 2 | | 2 010 010 <- |
+ * | | | 3 011 110 | <- |
+ * 3 -> | | | 4 100 001 | |
+ * -> | | 5 101 101 |
+ * -> | 6 110 011
+ * -> 7 111 111
+ */
+
#define _LGPL_SOURCE
+#define _GNU_SOURCE
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
+#include <sched.h>
+#include "config.h"
#include <urcu.h>
#include <urcu-call-rcu.h>
+#include <urcu-flavor.h>
#include <urcu/arch.h>
#include <urcu/uatomic.h>
-#include <urcu/jhash.h>
#include <urcu/compiler.h>
#include <urcu/rculfhash.h>
+#include <rculfhash-internal.h>
#include <stdio.h>
#include <pthread.h>
-#define DEBUG /* Test */
+/*
+ * Split-counters lazily update the global counter each 1024
+ * addition/removal. It automatically keeps track of resize required.
+ * We use the bucket length as indicator for need to expand for small
+ * tables and machines lacking per-cpu data support.
+ */
+#define COUNT_COMMIT_ORDER 10
+#define DEFAULT_SPLIT_COUNT_MASK 0xFUL
+#define CHAIN_LEN_TARGET 1
+#define CHAIN_LEN_RESIZE_THRESHOLD 3
-#ifdef DEBUG
-#define dbg_printf(args...) printf(args)
-#else
-#define dbg_printf(args...)
-#endif
+/*
+ * Define the minimum table size.
+ */
+#define MIN_TABLE_ORDER 0
+#define MIN_TABLE_SIZE (1UL << MIN_TABLE_ORDER)
-#define CHAIN_LEN_TARGET 4
-#define CHAIN_LEN_RESIZE_THRESHOLD 16
+/*
+ * Minimum number of bucket nodes to touch per thread to parallelize grow/shrink.
+ */
+#define MIN_PARTITION_PER_THREAD_ORDER 12
+#define MIN_PARTITION_PER_THREAD (1UL << MIN_PARTITION_PER_THREAD_ORDER)
-#ifndef max
-#define max(a, b) ((a) > (b) ? (a) : (b))
-#endif
+/*
+ * The removed flag needs to be updated atomically with the pointer.
+ * It indicates that no node must attach to the node scheduled for
+ * removal, and that node garbage collection must be performed.
+ * The bucket flag does not require to be updated atomically with the
+ * pointer, but it is added as a pointer low bit flag to save space.
+ * The "removal owner" flag is used to detect which of the "del"
+ * operation that has set the "removed flag" gets to return the removed
+ * node to its caller. Note that the replace operation does not need to
+ * iteract with the "removal owner" flag, because it validates that
+ * the "removed" flag is not set before performing its cmpxchg.
+ */
+#define REMOVED_FLAG (1UL << 0)
+#define BUCKET_FLAG (1UL << 1)
+#define REMOVAL_OWNER_FLAG (1UL << 2)
+#define FLAGS_MASK ((1UL << 3) - 1)
-struct rcu_table {
- unsigned long size; /* always a power of 2 */
- unsigned long resize_target;
- int resize_initiated;
- struct rcu_head head;
- struct rcu_ht_node *tbl[0];
-};
+/* Value of the end pointer. Should not interact with flags. */
+#define END_VALUE NULL
-struct rcu_ht {
- struct rcu_table *t; /* shared */
- ht_hash_fct hash_fct;
- ht_compare_fct compare_fct;
- unsigned long hash_seed;
- pthread_mutex_t resize_mutex; /* resize mutex: add/del mutex */
- void (*ht_call_rcu)(struct rcu_head *head,
- void (*func)(struct rcu_head *head));
-};
+/*
+ * ht_items_count: Split-counters counting the number of node addition
+ * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
+ * is set at hash table creation.
+ *
+ * These are free-running counters, never reset to zero. They count the
+ * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
+ * operations to update the global counter. We choose a power-of-2 value
+ * for the trigger to deal with 32 or 64-bit overflow of the counter.
+ */
+struct ht_items_count {
+ unsigned long add, del;
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+/*
+ * rcu_resize_work: Contains arguments passed to RCU worker thread
+ * responsible for performing lazy resize.
+ */
struct rcu_resize_work {
struct rcu_head head;
- struct rcu_ht *ht;
+ struct cds_lfht *ht;
+};
+
+/*
+ * partition_resize_work: Contains arguments passed to worker threads
+ * executing the hash table resize on partitions of the hash table
+ * assigned to each processor's worker thread.
+ */
+struct partition_resize_work {
+ pthread_t thread_id;
+ struct cds_lfht *ht;
+ unsigned long i, start, len;
+ void (*fct)(struct cds_lfht *ht, unsigned long i,
+ unsigned long start, unsigned long len);
};
/*
return BitReverseTable256[v];
}
-static __attribute__((unused))
+#if (CAA_BITS_PER_LONG == 32)
+static
uint32_t bit_reverse_u32(uint32_t v)
{
return ((uint32_t) bit_reverse_u8(v) << 24) |
((uint32_t) bit_reverse_u8(v >> 16) << 8) |
((uint32_t) bit_reverse_u8(v >> 24));
}
-
-static __attribute__((unused))
+#else
+static
uint64_t bit_reverse_u64(uint64_t v)
{
return ((uint64_t) bit_reverse_u8(v) << 56) |
((uint64_t) bit_reverse_u8(v >> 48) << 8) |
((uint64_t) bit_reverse_u8(v >> 56));
}
+#endif
static
unsigned long bit_reverse_ulong(unsigned long v)
}
/*
- * Algorithm to find the log2 of a 32-bit unsigned integer.
- * source: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogLookup
- * Originally from Public Domain.
+ * fls: returns the position of the most significant bit.
+ * Returns 0 if no bit is set, else returns the position of the most
+ * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
*/
-static const char LogTable256[256] =
+#if defined(__i386) || defined(__x86_64)
+static inline
+unsigned int fls_u32(uint32_t x)
{
-#define LT(n) n, n, n, n, n, n, n, n, n, n, n, n, n, n, n, n
- -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
- LT(4), LT(5), LT(5), LT(6), LT(6), LT(6), LT(6),
- LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7)
-};
+ int r;
+
+ asm("bsrl %1,%0\n\t"
+ "jnz 1f\n\t"
+ "movl $-1,%0\n\t"
+ "1:\n\t"
+ : "=r" (r) : "rm" (x));
+ return r + 1;
+}
+#define HAS_FLS_U32
+#endif
-uint32_t log2_u32(uint32_t v)
+#if defined(__x86_64)
+static inline
+unsigned int fls_u64(uint64_t x)
{
- uint32_t t, tt;
+ long r;
- if ((tt = (v >> 16)))
- return (t = (tt >> 8))
- ? 24 + LogTable256[t]
- : 16 + LogTable256[tt];
- else
- return (t = (v >> 8))
- ? 8 + LogTable256[t]
- : LogTable256[v];
+ asm("bsrq %1,%0\n\t"
+ "jnz 1f\n\t"
+ "movq $-1,%0\n\t"
+ "1:\n\t"
+ : "=r" (r) : "rm" (x));
+ return r + 1;
}
+#define HAS_FLS_U64
+#endif
-static
-void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth);
-
-static
-void check_resize(struct rcu_ht *ht, struct rcu_table *t,
- uint32_t chain_len)
+#ifndef HAS_FLS_U64
+static __attribute__((unused))
+unsigned int fls_u64(uint64_t x)
{
- if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
- ht_resize_lazy(ht, t,
- log2_u32(chain_len - CHAIN_LEN_TARGET));
+ unsigned int r = 64;
+
+ if (!x)
+ return 0;
+
+ if (!(x & 0xFFFFFFFF00000000ULL)) {
+ x <<= 32;
+ r -= 32;
+ }
+ if (!(x & 0xFFFF000000000000ULL)) {
+ x <<= 16;
+ r -= 16;
+ }
+ if (!(x & 0xFF00000000000000ULL)) {
+ x <<= 8;
+ r -= 8;
+ }
+ if (!(x & 0xF000000000000000ULL)) {
+ x <<= 4;
+ r -= 4;
+ }
+ if (!(x & 0xC000000000000000ULL)) {
+ x <<= 2;
+ r -= 2;
+ }
+ if (!(x & 0x8000000000000000ULL)) {
+ x <<= 1;
+ r -= 1;
+ }
+ return r;
}
+#endif
-static
-struct rcu_ht_node *clear_flag(struct rcu_ht_node *node)
+#ifndef HAS_FLS_U32
+static __attribute__((unused))
+unsigned int fls_u32(uint32_t x)
{
- return (struct rcu_ht_node *) (((unsigned long) node) & ~0x1);
+ unsigned int r = 32;
+
+ if (!x)
+ return 0;
+ if (!(x & 0xFFFF0000U)) {
+ x <<= 16;
+ r -= 16;
+ }
+ if (!(x & 0xFF000000U)) {
+ x <<= 8;
+ r -= 8;
+ }
+ if (!(x & 0xF0000000U)) {
+ x <<= 4;
+ r -= 4;
+ }
+ if (!(x & 0xC0000000U)) {
+ x <<= 2;
+ r -= 2;
+ }
+ if (!(x & 0x80000000U)) {
+ x <<= 1;
+ r -= 1;
+ }
+ return r;
}
+#endif
-static
-int is_removed(struct rcu_ht_node *node)
+unsigned int cds_lfht_fls_ulong(unsigned long x)
{
- return ((unsigned long) node) & 0x1;
+#if (CAA_BITS_PER_LONG == 32)
+ return fls_u32(x);
+#else
+ return fls_u64(x);
+#endif
}
-static
-struct rcu_ht_node *flag_removed(struct rcu_ht_node *node)
+/*
+ * Return the minimum order for which x <= (1UL << order).
+ * Return -1 if x is 0.
+ */
+int cds_lfht_get_count_order_u32(uint32_t x)
{
- return (struct rcu_ht_node *) (((unsigned long) node) | 0x1);
+ if (!x)
+ return -1;
+
+ return fls_u32(x - 1);
}
-static
-unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
+/*
+ * Return the minimum order for which x <= (1UL << order).
+ * Return -1 if x is 0.
+ */
+int cds_lfht_get_count_order_ulong(unsigned long x)
{
- unsigned long old1, old2;
+ if (!x)
+ return -1;
- old1 = uatomic_read(ptr);
- do {
- old2 = old1;
- if (old2 >= v)
- return old2;
- } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
- return v;
+ return cds_lfht_fls_ulong(x - 1);
}
static
-void _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
-{
- struct rcu_ht_node *iter_prev, *iter, *iter_prev_next, *next;
+void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth);
- if (!t->size)
- return;
- for (;;) {
- uint32_t chain_len = 0;
+static
+void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
+ unsigned long count);
- /*
- * iter_prev points to the non-removed node prior to the
- * insert location.
- * iter iterates until it finds the next non-removed
- * node.
- */
- iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
- /* We can always skip the dummy node initially */
- iter_prev_next = next = rcu_dereference(iter_prev->next);
- assert(iter_prev);
- assert(iter_prev->reverse_hash <= node->reverse_hash);
- for (;;) {
- iter = next;
- if (unlikely(!clear_flag(iter)))
- break;
- next = rcu_dereference(clear_flag(iter)->next);
- if (unlikely(is_removed(next)))
- continue;
- if (clear_flag(iter)->reverse_hash > node->reverse_hash)
- break;
- /* Only account for identical reverse hash once */
- if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash)
- check_resize(ht, t, ++chain_len);
- iter_prev = clear_flag(iter);
- iter_prev_next = next;
- }
- assert(node != iter);
- assert(!is_removed(iter_prev));
- assert(iter_prev != node);
- node->next = iter;
- if (uatomic_cmpxchg(&iter_prev->next, iter_prev_next,
- node) != iter_prev_next)
- continue;
- else
- break;
- }
-}
+static long nr_cpus_mask = -1;
+static long split_count_mask = -1;
-static
-int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
+#if defined(HAVE_SYSCONF)
+static void ht_init_nr_cpus_mask(void)
{
- struct rcu_ht_node *iter_prev, *iter, *iter_prev_next, *next, *old;
- unsigned long chain_len;
- int found;
- int flagged = 0;
+ long maxcpus;
-retry:
- chain_len = 0;
- found = 0;
- /*
- * iter_prev points to the non-removed node prior to the remove
- * location.
- * node is the node to remove.
- */
- iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
- /* We can always skip the dummy node initially */
- iter_prev_next = next = rcu_dereference(iter_prev->next);
- assert(iter_prev);
- assert(iter_prev->reverse_hash <= node->reverse_hash);
- for (;;) {
- iter = next;
- if (unlikely(!clear_flag(iter)))
- break;
- next = rcu_dereference(clear_flag(iter)->next);
- if (iter == node) {
- found = 1;
- break;
- }
- if (unlikely(is_removed(next)))
- continue;
- if (clear_flag(iter)->reverse_hash > node->reverse_hash)
- break;
- iter_prev = clear_flag(iter);
- iter_prev_next = next;
- }
- if (!found)
- goto end;
- if (!flagged) {
- if (is_removed(next))
- goto end;
- /* set deletion flag */
- if ((old = uatomic_cmpxchg(&iter->next, next,
- flag_removed(next))) != next) {
- if (old == flag_removed(next))
- goto end;
- else
- goto retry;
- }
- flagged = 1;
+ maxcpus = sysconf(_SC_NPROCESSORS_CONF);
+ if (maxcpus <= 0) {
+ nr_cpus_mask = -2;
+ return;
}
/*
- * Remove the element from the list.
- * - Retry if there has been a concurrent add before us.
- * - Retry if the prev node has been deleted (its next removed
- * flag would be set).
- * - There cannot be a concurrent delete for our position, because
- * we won the deletion flag cmpxchg.
- * - If there is a concurrent add or remove after us while our
- * removed flag is set, it will skip us and link directly after
- * the prior non-removed node before us. In this case, the
- * retry will not find the node in the list anymore.
- */
- if (uatomic_cmpxchg(&iter_prev->next, iter_prev_next,
- clear_flag(next)) != iter_prev_next)
- goto retry;
-end:
- /*
- * Only the flagging action indicated that we (and no other)
- * removed the node from the hash.
+ * round up number of CPUs to next power of two, so we
+ * can use & for modulo.
*/
- if (flagged)
- return 0;
- else
- return -ENOENT;
+ maxcpus = 1UL << cds_lfht_get_count_order_ulong(maxcpus);
+ nr_cpus_mask = maxcpus - 1;
}
+#else /* #if defined(HAVE_SYSCONF) */
+static void ht_init_nr_cpus_mask(void)
+{
+ nr_cpus_mask = -2;
+}
+#endif /* #else #if defined(HAVE_SYSCONF) */
static
-void init_table(struct rcu_ht *ht, struct rcu_table *t,
- unsigned long first, unsigned long len)
+void alloc_split_items_count(struct cds_lfht *ht)
{
- unsigned long i, end;
+ if (nr_cpus_mask == -1) {
+ ht_init_nr_cpus_mask();
+ if (nr_cpus_mask < 0)
+ split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
+ else
+ split_count_mask = nr_cpus_mask;
+ }
- end = first + len;
- for (i = first; i < end; i++) {
- /* Update table size when power of two */
- if (i != 0 && !(i & (i - 1)))
- t->size = i;
- t->tbl[i] = calloc(1, sizeof(struct rcu_ht_node));
- t->tbl[i]->dummy = 1;
- t->tbl[i]->hash = i;
- t->tbl[i]->reverse_hash = bit_reverse_ulong(i);
- _ht_add(ht, t, t->tbl[i]);
+ assert(split_count_mask >= 0);
+
+ if (ht->flags & CDS_LFHT_ACCOUNTING) {
+ ht->split_count = calloc(split_count_mask + 1,
+ sizeof(struct ht_items_count));
+ assert(ht->split_count);
+ } else {
+ ht->split_count = NULL;
}
- t->resize_target = t->size = end;
- t->resize_initiated = 0;
}
-struct rcu_ht *ht_new(ht_hash_fct hash_fct,
- ht_compare_fct compare_fct,
- unsigned long hash_seed,
- unsigned long init_size,
- void (*ht_call_rcu)(struct rcu_head *head,
- void (*func)(struct rcu_head *head)))
+static
+void free_split_items_count(struct cds_lfht *ht)
{
- struct rcu_ht *ht;
+ poison_free(ht->split_count);
+}
- ht = calloc(1, sizeof(struct rcu_ht));
- ht->hash_fct = hash_fct;
- ht->compare_fct = compare_fct;
- ht->hash_seed = hash_seed;
- ht->ht_call_rcu = ht_call_rcu;
- /* this mutex should not nest in read-side C.S. */
- pthread_mutex_init(&ht->resize_mutex, NULL);
- ht->t = calloc(1, sizeof(struct rcu_table)
- + (max(init_size, 1) * sizeof(struct rcu_ht_node *)));
- ht->t->size = 0;
- pthread_mutex_lock(&ht->resize_mutex);
- init_table(ht, ht->t, 0, max(init_size, 1));
- pthread_mutex_unlock(&ht->resize_mutex);
- return ht;
+#if defined(HAVE_SCHED_GETCPU)
+static
+int ht_get_split_count_index(unsigned long hash)
+{
+ int cpu;
+
+ assert(split_count_mask >= 0);
+ cpu = sched_getcpu();
+ if (caa_unlikely(cpu < 0))
+ return hash & split_count_mask;
+ else
+ return cpu & split_count_mask;
}
+#else /* #if defined(HAVE_SCHED_GETCPU) */
+static
+int ht_get_split_count_index(unsigned long hash)
+{
+ return hash & split_count_mask;
+}
+#endif /* #else #if defined(HAVE_SCHED_GETCPU) */
-struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
+static
+void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
{
- struct rcu_table *t;
- struct rcu_ht_node *node;
- unsigned long hash, reverse_hash;
+ unsigned long split_count;
+ int index;
+ long count;
- hash = ht->hash_fct(key, key_len, ht->hash_seed);
- reverse_hash = bit_reverse_ulong(hash);
+ if (caa_unlikely(!ht->split_count))
+ return;
+ index = ht_get_split_count_index(hash);
+ split_count = uatomic_add_return(&ht->split_count[index].add, 1);
+ if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
+ return;
+ /* Only if number of add multiple of 1UL << COUNT_COMMIT_ORDER */
- t = rcu_dereference(ht->t);
- node = rcu_dereference(t->tbl[hash & (t->size - 1)]);
- for (;;) {
- if (unlikely(!node))
- break;
- if (unlikely(node->reverse_hash > reverse_hash)) {
- node = NULL;
- break;
- }
- if (!ht->compare_fct(node->key, node->key_len, key, key_len)) {
- if (unlikely(is_removed(rcu_dereference(node->next))))
- node = NULL;
- break;
- }
- node = clear_flag(rcu_dereference(node->next));
- }
- return node;
+ dbg_printf("add split count %lu\n", split_count);
+ count = uatomic_add_return(&ht->count,
+ 1UL << COUNT_COMMIT_ORDER);
+ if (caa_likely(count & (count - 1)))
+ return;
+ /* Only if global count is power of 2 */
+
+ if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) < size)
+ return;
+ dbg_printf("add set global %ld\n", count);
+ cds_lfht_resize_lazy_count(ht, size,
+ count >> (CHAIN_LEN_TARGET - 1));
}
-void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
+static
+void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
{
- struct rcu_table *t;
+ unsigned long split_count;
+ int index;
+ long count;
+
+ if (caa_unlikely(!ht->split_count))
+ return;
+ index = ht_get_split_count_index(hash);
+ split_count = uatomic_add_return(&ht->split_count[index].del, 1);
+ if (caa_likely(split_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))
+ return;
+ /* Only if number of deletes multiple of 1UL << COUNT_COMMIT_ORDER */
- node->hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
- node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
+ dbg_printf("del split count %lu\n", split_count);
+ count = uatomic_add_return(&ht->count,
+ -(1UL << COUNT_COMMIT_ORDER));
+ if (caa_likely(count & (count - 1)))
+ return;
+ /* Only if global count is power of 2 */
- t = rcu_dereference(ht->t);
- _ht_add(ht, t, node);
+ if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size)
+ return;
+ dbg_printf("del set global %ld\n", count);
+ /*
+ * Don't shrink table if the number of nodes is below a
+ * certain threshold.
+ */
+ if (count < (1UL << COUNT_COMMIT_ORDER) * (split_count_mask + 1))
+ return;
+ cds_lfht_resize_lazy_count(ht, size,
+ count >> (CHAIN_LEN_TARGET - 1));
}
-int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node)
+static
+void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
{
- struct rcu_table *t;
+ unsigned long count;
- t = rcu_dereference(ht->t);
- return _ht_remove(ht, t, node);
+ if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
+ return;
+ count = uatomic_read(&ht->count);
+ /*
+ * Use bucket-local length for small table expand and for
+ * environments lacking per-cpu data support.
+ */
+ if (count >= (1UL << COUNT_COMMIT_ORDER))
+ return;
+ if (chain_len > 100)
+ dbg_printf("WARNING: large chain length: %u.\n",
+ chain_len);
+ if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
+ cds_lfht_resize_lazy_grow(ht, size,
+ cds_lfht_get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
}
static
-int ht_delete_dummy(struct rcu_ht *ht)
+struct cds_lfht_node *clear_flag(struct cds_lfht_node *node)
{
- struct rcu_table *t;
- struct rcu_ht_node *node;
- unsigned long i;
+ return (struct cds_lfht_node *) (((unsigned long) node) & ~FLAGS_MASK);
+}
- t = ht->t;
- /* Check that the table is empty */
- node = t->tbl[0];
- do {
- if (!node->dummy)
- return -EPERM;
- node = node->next;
- } while (node);
- /* Internal sanity check: all nodes left should be dummy */
- for (i = 0; i < t->size; i++) {
- assert(t->tbl[i]->dummy);
- free(t->tbl[i]);
- }
- return 0;
+static
+int is_removed(struct cds_lfht_node *node)
+{
+ return ((unsigned long) node) & REMOVED_FLAG;
}
-/*
- * Should only be called when no more concurrent readers nor writers can
- * possibly access the table.
- */
-int ht_destroy(struct rcu_ht *ht)
+static
+int is_bucket(struct cds_lfht_node *node)
{
- int ret;
+ return ((unsigned long) node) & BUCKET_FLAG;
+}
- ret = ht_delete_dummy(ht);
- if (ret)
- return ret;
- free(ht->t);
- free(ht);
- return ret;
+static
+struct cds_lfht_node *flag_bucket(struct cds_lfht_node *node)
+{
+ return (struct cds_lfht_node *) (((unsigned long) node) | BUCKET_FLAG);
}
static
-void ht_free_table_cb(struct rcu_head *head)
+int is_removal_owner(struct cds_lfht_node *node)
{
- struct rcu_table *t =
- caa_container_of(head, struct rcu_table, head);
- free(t);
+ return ((unsigned long) node) & REMOVAL_OWNER_FLAG;
}
-/* called with resize mutex held */
static
-void _do_ht_resize(struct rcu_ht *ht)
+struct cds_lfht_node *flag_removal_owner(struct cds_lfht_node *node)
{
- unsigned long new_size, old_size;
- struct rcu_table *new_t, *old_t;
+ return (struct cds_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG);
+}
- old_t = ht->t;
- old_size = old_t->size;
+static
+struct cds_lfht_node *flag_removed_or_removal_owner(struct cds_lfht_node *node)
+{
+ return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG | REMOVAL_OWNER_FLAG);
+}
- new_size = CMM_LOAD_SHARED(old_t->resize_target);
- dbg_printf("rculfhash: resize from %lu to %lu buckets\n",
- old_size, new_size);
- if (old_size == new_size)
- return;
- new_t = malloc(sizeof(struct rcu_table)
- + (new_size * sizeof(struct rcu_ht_node *)));
- assert(new_size > old_size);
- memcpy(&new_t->tbl, &old_t->tbl,
- old_size * sizeof(struct rcu_ht_node *));
- init_table(ht, new_t, old_size, new_size - old_size);
- /* Changing table and size atomically wrt lookups */
- rcu_assign_pointer(ht->t, new_t);
- ht->ht_call_rcu(&old_t->head, ht_free_table_cb);
+static
+struct cds_lfht_node *get_end(void)
+{
+ return (struct cds_lfht_node *) END_VALUE;
}
static
-unsigned long resize_target_update(struct rcu_table *t,
- int growth_order)
+int is_end(struct cds_lfht_node *node)
{
- return _uatomic_max(&t->resize_target,
- t->size << growth_order);
+ return clear_flag(node) == (struct cds_lfht_node *) END_VALUE;
}
-void ht_resize(struct rcu_ht *ht, int growth)
+static
+unsigned long _uatomic_xchg_monotonic_increase(unsigned long *ptr,
+ unsigned long v)
{
- struct rcu_table *t = rcu_dereference(ht->t);
- unsigned long target_size;
+ unsigned long old1, old2;
- target_size = resize_target_update(t, growth);
- if (t->size < target_size) {
- CMM_STORE_SHARED(t->resize_initiated, 1);
- pthread_mutex_lock(&ht->resize_mutex);
- _do_ht_resize(ht);
- pthread_mutex_unlock(&ht->resize_mutex);
- }
+ old1 = uatomic_read(ptr);
+ do {
+ old2 = old1;
+ if (old2 >= v)
+ return old2;
+ } while ((old1 = uatomic_cmpxchg(ptr, old2, v)) != old2);
+ return old2;
}
static
-void do_resize_cb(struct rcu_head *head)
+void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
{
- struct rcu_resize_work *work =
- caa_container_of(head, struct rcu_resize_work, head);
- struct rcu_ht *ht = work->ht;
+ return ht->mm->alloc_bucket_table(ht, order);
+}
- pthread_mutex_lock(&ht->resize_mutex);
- _do_ht_resize(ht);
- pthread_mutex_unlock(&ht->resize_mutex);
- free(work);
+/*
+ * cds_lfht_free_bucket_table() should be called with decreasing order.
+ * When cds_lfht_free_bucket_table(0) is called, it means the whole
+ * lfht is destroyed.
+ */
+static
+void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
+{
+ return ht->mm->free_bucket_table(ht, order);
+}
+
+static inline
+struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
+{
+ return ht->bucket_at(ht, index);
+}
+
+static inline
+struct cds_lfht_node *lookup_bucket(struct cds_lfht *ht, unsigned long size,
+ unsigned long hash)
+{
+ assert(size > 0);
+ return bucket_at(ht, hash & (size - 1));
}
+/*
+ * Remove all logically deleted nodes from a bucket up to a certain node key.
+ */
static
-void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth)
+void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *node)
{
- struct rcu_resize_work *work;
- unsigned long target_size;
+ struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
- target_size = resize_target_update(t, growth);
- if (!CMM_LOAD_SHARED(t->resize_initiated) && t->size < target_size) {
- work = malloc(sizeof(*work));
- work->ht = ht;
- ht->ht_call_rcu(&work->head, do_resize_cb);
- CMM_STORE_SHARED(t->resize_initiated, 1);
+ assert(!is_bucket(bucket));
+ assert(!is_removed(bucket));
+ assert(!is_bucket(node));
+ assert(!is_removed(node));
+ for (;;) {
+ iter_prev = bucket;
+ /* We can always skip the bucket node initially */
+ iter = rcu_dereference(iter_prev->next);
+ assert(!is_removed(iter));
+ assert(iter_prev->reverse_hash <= node->reverse_hash);
+ /*
+ * We should never be called with bucket (start of chain)
+ * and logically removed node (end of path compression
+ * marker) being the actual same node. This would be a
+ * bug in the algorithm implementation.
+ */
+ assert(bucket != node);
+ for (;;) {
+ if (caa_unlikely(is_end(iter)))
+ return;
+ if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
+ return;
+ next = rcu_dereference(clear_flag(iter)->next);
+ if (caa_likely(is_removed(next)))
+ break;
+ iter_prev = clear_flag(iter);
+ iter = next;
+ }
+ assert(!is_removed(iter));
+ if (is_bucket(iter))
+ new_next = flag_bucket(clear_flag(next));
+ else
+ new_next = clear_flag(next);
+ (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
+ }
+}
+
+static
+int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
+ struct cds_lfht_node *old_node,
+ struct cds_lfht_node *old_next,
+ struct cds_lfht_node *new_node)
+{
+ struct cds_lfht_node *bucket, *ret_next;
+
+ if (!old_node) /* Return -ENOENT if asked to replace NULL node */
+ return -ENOENT;
+
+ assert(!is_removed(old_node));
+ assert(!is_bucket(old_node));
+ assert(!is_removed(new_node));
+ assert(!is_bucket(new_node));
+ assert(new_node != old_node);
+ for (;;) {
+ /* Insert after node to be replaced */
+ if (is_removed(old_next)) {
+ /*
+ * Too late, the old node has been removed under us
+ * between lookup and replace. Fail.
+ */
+ return -ENOENT;
+ }
+ assert(old_next == clear_flag(old_next));
+ assert(new_node != old_next);
+ /*
+ * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED
+ * flag. It is either set atomically at the same time
+ * (replace) or after (del).
+ */
+ assert(!is_removal_owner(old_next));
+ new_node->next = old_next;
+ /*
+ * Here is the whole trick for lock-free replace: we add
+ * the replacement node _after_ the node we want to
+ * replace by atomically setting its next pointer at the
+ * same time we set its removal flag. Given that
+ * the lookups/get next use an iterator aware of the
+ * next pointer, they will either skip the old node due
+ * to the removal flag and see the new node, or use
+ * the old node, but will not see the new one.
+ * This is a replacement of a node with another node
+ * that has the same value: we are therefore not
+ * removing a value from the hash table. We set both the
+ * REMOVED and REMOVAL_OWNER flags atomically so we own
+ * the node after successful cmpxchg.
+ */
+ ret_next = uatomic_cmpxchg(&old_node->next,
+ old_next, flag_removed_or_removal_owner(new_node));
+ if (ret_next == old_next)
+ break; /* We performed the replacement. */
+ old_next = ret_next;
+ }
+
+ /*
+ * Ensure that the old node is not visible to readers anymore:
+ * lookup for the node, and remove it (along with any other
+ * logically removed node) if found.
+ */
+ bucket = lookup_bucket(ht, size, bit_reverse_ulong(old_node->reverse_hash));
+ _cds_lfht_gc_bucket(bucket, new_node);
+
+ assert(is_removed(CMM_LOAD_SHARED(old_node->next)));
+ return 0;
+}
+
+/*
+ * A non-NULL unique_ret pointer uses the "add unique" (or uniquify) add
+ * mode. A NULL unique_ret allows creation of duplicate keys.
+ */
+static
+void _cds_lfht_add(struct cds_lfht *ht,
+ unsigned long hash,
+ cds_lfht_match_fct match,
+ const void *key,
+ unsigned long size,
+ struct cds_lfht_node *node,
+ struct cds_lfht_iter *unique_ret,
+ int bucket_flag)
+{
+ struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
+ *return_node;
+ struct cds_lfht_node *bucket;
+
+ assert(!is_bucket(node));
+ assert(!is_removed(node));
+ bucket = lookup_bucket(ht, size, hash);
+ for (;;) {
+ uint32_t chain_len = 0;
+
+ /*
+ * iter_prev points to the non-removed node prior to the
+ * insert location.
+ */
+ iter_prev = bucket;
+ /* We can always skip the bucket node initially */
+ iter = rcu_dereference(iter_prev->next);
+ assert(iter_prev->reverse_hash <= node->reverse_hash);
+ for (;;) {
+ if (caa_unlikely(is_end(iter)))
+ goto insert;
+ if (caa_likely(clear_flag(iter)->reverse_hash > node->reverse_hash))
+ goto insert;
+
+ /* bucket node is the first node of the identical-hash-value chain */
+ if (bucket_flag && clear_flag(iter)->reverse_hash == node->reverse_hash)
+ goto insert;
+
+ next = rcu_dereference(clear_flag(iter)->next);
+ if (caa_unlikely(is_removed(next)))
+ goto gc_node;
+
+ /* uniquely add */
+ if (unique_ret
+ && !is_bucket(next)
+ && clear_flag(iter)->reverse_hash == node->reverse_hash) {
+ struct cds_lfht_iter d_iter = { .node = node, .next = iter, };
+
+ /*
+ * uniquely adding inserts the node as the first
+ * node of the identical-hash-value node chain.
+ *
+ * This semantic ensures no duplicated keys
+ * should ever be observable in the table
+ * (including traversing the table node by
+ * node by forward iterations)
+ */
+ cds_lfht_next_duplicate(ht, match, key, &d_iter);
+ if (!d_iter.node)
+ goto insert;
+
+ *unique_ret = d_iter;
+ return;
+ }
+
+ /* Only account for identical reverse hash once */
+ if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash
+ && !is_bucket(next))
+ check_resize(ht, size, ++chain_len);
+ iter_prev = clear_flag(iter);
+ iter = next;
+ }
+
+ insert:
+ assert(node != clear_flag(iter));
+ assert(!is_removed(iter_prev));
+ assert(!is_removed(iter));
+ assert(iter_prev != node);
+ if (!bucket_flag)
+ node->next = clear_flag(iter);
+ else
+ node->next = flag_bucket(clear_flag(iter));
+ if (is_bucket(iter))
+ new_node = flag_bucket(node);
+ else
+ new_node = node;
+ if (uatomic_cmpxchg(&iter_prev->next, iter,
+ new_node) != iter) {
+ continue; /* retry */
+ } else {
+ return_node = node;
+ goto end;
+ }
+
+ gc_node:
+ assert(!is_removed(iter));
+ if (is_bucket(iter))
+ new_next = flag_bucket(clear_flag(next));
+ else
+ new_next = clear_flag(next);
+ (void) uatomic_cmpxchg(&iter_prev->next, iter, new_next);
+ /* retry */
+ }
+end:
+ if (unique_ret) {
+ unique_ret->node = return_node;
+ /* unique_ret->next left unset, never used. */
+ }
+}
+
+static
+int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
+ struct cds_lfht_node *node)
+{
+ struct cds_lfht_node *bucket, *next;
+
+ if (!node) /* Return -ENOENT if asked to delete NULL node */
+ return -ENOENT;
+
+ /* logically delete the node */
+ assert(!is_bucket(node));
+ assert(!is_removed(node));
+ assert(!is_removal_owner(node));
+
+ /*
+ * We are first checking if the node had previously been
+ * logically removed (this check is not atomic with setting the
+ * logical removal flag). Return -ENOENT if the node had
+ * previously been removed.
+ */
+ next = CMM_LOAD_SHARED(node->next); /* next is not dereferenced */
+ if (caa_unlikely(is_removed(next)))
+ return -ENOENT;
+ assert(!is_bucket(next));
+ /*
+ * The del operation semantic guarantees a full memory barrier
+ * before the uatomic_or atomic commit of the deletion flag.
+ */
+ cmm_smp_mb__before_uatomic_or();
+ /*
+ * We set the REMOVED_FLAG unconditionally. Note that there may
+ * be more than one concurrent thread setting this flag.
+ * Knowing which wins the race will be known after the garbage
+ * collection phase, stay tuned!
+ */
+ uatomic_or(&node->next, REMOVED_FLAG);
+ /* We performed the (logical) deletion. */
+
+ /*
+ * Ensure that the node is not visible to readers anymore: lookup for
+ * the node, and remove it (along with any other logically removed node)
+ * if found.
+ */
+ bucket = lookup_bucket(ht, size, bit_reverse_ulong(node->reverse_hash));
+ _cds_lfht_gc_bucket(bucket, node);
+
+ assert(is_removed(CMM_LOAD_SHARED(node->next)));
+ /*
+ * Last phase: atomically exchange node->next with a version
+ * having "REMOVAL_OWNER_FLAG" set. If the returned node->next
+ * pointer did _not_ have "REMOVAL_OWNER_FLAG" set, we now own
+ * the node and win the removal race.
+ * It is interesting to note that all "add" paths are forbidden
+ * to change the next pointer starting from the point where the
+ * REMOVED_FLAG is set, so here using a read, followed by a
+ * xchg() suffice to guarantee that the xchg() will ever only
+ * set the "REMOVAL_OWNER_FLAG" (or change nothing if the flag
+ * was already set).
+ */
+ if (!is_removal_owner(uatomic_xchg(&node->next,
+ flag_removal_owner(node->next))))
+ return 0;
+ else
+ return -ENOENT;
+}
+
+static
+void *partition_resize_thread(void *arg)
+{
+ struct partition_resize_work *work = arg;
+
+ work->ht->flavor->register_thread();
+ work->fct(work->ht, work->i, work->start, work->len);
+ work->ht->flavor->unregister_thread();
+ return NULL;
+}
+
+static
+void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
+ unsigned long len,
+ void (*fct)(struct cds_lfht *ht, unsigned long i,
+ unsigned long start, unsigned long len))
+{
+ unsigned long partition_len;
+ struct partition_resize_work *work;
+ int thread, ret;
+ unsigned long nr_threads;
+
+ /*
+ * Note: nr_cpus_mask + 1 is always power of 2.
+ * We spawn just the number of threads we need to satisfy the minimum
+ * partition size, up to the number of CPUs in the system.
+ */
+ if (nr_cpus_mask > 0) {
+ nr_threads = min(nr_cpus_mask + 1,
+ len >> MIN_PARTITION_PER_THREAD_ORDER);
+ } else {
+ nr_threads = 1;
+ }
+ partition_len = len >> cds_lfht_get_count_order_ulong(nr_threads);
+ work = calloc(nr_threads, sizeof(*work));
+ assert(work);
+ for (thread = 0; thread < nr_threads; thread++) {
+ work[thread].ht = ht;
+ work[thread].i = i;
+ work[thread].len = partition_len;
+ work[thread].start = thread * partition_len;
+ work[thread].fct = fct;
+ ret = pthread_create(&(work[thread].thread_id), ht->resize_attr,
+ partition_resize_thread, &work[thread]);
+ assert(!ret);
+ }
+ for (thread = 0; thread < nr_threads; thread++) {
+ ret = pthread_join(work[thread].thread_id, NULL);
+ assert(!ret);
+ }
+ free(work);
+}
+
+/*
+ * Holding RCU read lock to protect _cds_lfht_add against memory
+ * reclaim that could be performed by other call_rcu worker threads (ABA
+ * problem).
+ *
+ * When we reach a certain length, we can split this population phase over
+ * many worker threads, based on the number of CPUs available in the system.
+ * This should therefore take care of not having the expand lagging behind too
+ * many concurrent insertion threads by using the scheduler's ability to
+ * schedule bucket node population fairly with insertions.
+ */
+static
+void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
+ unsigned long start, unsigned long len)
+{
+ unsigned long j, size = 1UL << (i - 1);
+
+ assert(i > MIN_TABLE_ORDER);
+ ht->flavor->read_lock();
+ for (j = size + start; j < size + start + len; j++) {
+ struct cds_lfht_node *new_node = bucket_at(ht, j);
+
+ assert(j >= size && j < (size << 1));
+ dbg_printf("init populate: order %lu index %lu hash %lu\n",
+ i, j, j);
+ new_node->reverse_hash = bit_reverse_ulong(j);
+ _cds_lfht_add(ht, j, NULL, NULL, size, new_node, NULL, 1);
+ }
+ ht->flavor->read_unlock();
+}
+
+static
+void init_table_populate(struct cds_lfht *ht, unsigned long i,
+ unsigned long len)
+{
+ assert(nr_cpus_mask != -1);
+ if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) {
+ ht->flavor->thread_online();
+ init_table_populate_partition(ht, i, 0, len);
+ ht->flavor->thread_offline();
+ return;
+ }
+ partition_resize_helper(ht, i, len, init_table_populate_partition);
+}
+
+static
+void init_table(struct cds_lfht *ht,
+ unsigned long first_order, unsigned long last_order)
+{
+ unsigned long i;
+
+ dbg_printf("init table: first_order %lu last_order %lu\n",
+ first_order, last_order);
+ assert(first_order > MIN_TABLE_ORDER);
+ for (i = first_order; i <= last_order; i++) {
+ unsigned long len;
+
+ len = 1UL << (i - 1);
+ dbg_printf("init order %lu len: %lu\n", i, len);
+
+ /* Stop expand if the resize target changes under us */
+ if (CMM_LOAD_SHARED(ht->resize_target) < (1UL << i))
+ break;
+
+ cds_lfht_alloc_bucket_table(ht, i);
+
+ /*
+ * Set all bucket nodes reverse hash values for a level and
+ * link all bucket nodes into the table.
+ */
+ init_table_populate(ht, i, len);
+
+ /*
+ * Update table size.
+ */
+ cmm_smp_wmb(); /* populate data before RCU size */
+ CMM_STORE_SHARED(ht->size, 1UL << i);
+
+ dbg_printf("init new size: %lu\n", 1UL << i);
+ if (CMM_LOAD_SHARED(ht->in_progress_destroy))
+ break;
+ }
+}
+
+/*
+ * Holding RCU read lock to protect _cds_lfht_remove against memory
+ * reclaim that could be performed by other call_rcu worker threads (ABA
+ * problem).
+ * For a single level, we logically remove and garbage collect each node.
+ *
+ * As a design choice, we perform logical removal and garbage collection on a
+ * node-per-node basis to simplify this algorithm. We also assume keeping good
+ * cache locality of the operation would overweight possible performance gain
+ * that could be achieved by batching garbage collection for multiple levels.
+ * However, this would have to be justified by benchmarks.
+ *
+ * Concurrent removal and add operations are helping us perform garbage
+ * collection of logically removed nodes. We guarantee that all logically
+ * removed nodes have been garbage-collected (unlinked) before call_rcu is
+ * invoked to free a hole level of bucket nodes (after a grace period).
+ *
+ * Logical removal and garbage collection can therefore be done in batch
+ * or on a node-per-node basis, as long as the guarantee above holds.
+ *
+ * When we reach a certain length, we can split this removal over many worker
+ * threads, based on the number of CPUs available in the system. This should
+ * take care of not letting resize process lag behind too many concurrent
+ * updater threads actively inserting into the hash table.
+ */
+static
+void remove_table_partition(struct cds_lfht *ht, unsigned long i,
+ unsigned long start, unsigned long len)
+{
+ unsigned long j, size = 1UL << (i - 1);
+
+ assert(i > MIN_TABLE_ORDER);
+ ht->flavor->read_lock();
+ for (j = size + start; j < size + start + len; j++) {
+ struct cds_lfht_node *fini_bucket = bucket_at(ht, j);
+ struct cds_lfht_node *parent_bucket = bucket_at(ht, j - size);
+
+ assert(j >= size && j < (size << 1));
+ dbg_printf("remove entry: order %lu index %lu hash %lu\n",
+ i, j, j);
+ /* Set the REMOVED_FLAG to freeze the ->next for gc */
+ uatomic_or(&fini_bucket->next, REMOVED_FLAG);
+ _cds_lfht_gc_bucket(parent_bucket, fini_bucket);
+ }
+ ht->flavor->read_unlock();
+}
+
+static
+void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
+{
+
+ assert(nr_cpus_mask != -1);
+ if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) {
+ ht->flavor->thread_online();
+ remove_table_partition(ht, i, 0, len);
+ ht->flavor->thread_offline();
+ return;
+ }
+ partition_resize_helper(ht, i, len, remove_table_partition);
+}
+
+/*
+ * fini_table() is never called for first_order == 0, which is why
+ * free_by_rcu_order == 0 can be used as criterion to know if free must
+ * be called.
+ */
+static
+void fini_table(struct cds_lfht *ht,
+ unsigned long first_order, unsigned long last_order)
+{
+ long i;
+ unsigned long free_by_rcu_order = 0;
+
+ dbg_printf("fini table: first_order %lu last_order %lu\n",
+ first_order, last_order);
+ assert(first_order > MIN_TABLE_ORDER);
+ for (i = last_order; i >= first_order; i--) {
+ unsigned long len;
+
+ len = 1UL << (i - 1);
+ dbg_printf("fini order %lu len: %lu\n", i, len);
+
+ /* Stop shrink if the resize target changes under us */
+ if (CMM_LOAD_SHARED(ht->resize_target) > (1UL << (i - 1)))
+ break;
+
+ cmm_smp_wmb(); /* populate data before RCU size */
+ CMM_STORE_SHARED(ht->size, 1UL << (i - 1));
+
+ /*
+ * We need to wait for all add operations to reach Q.S. (and
+ * thus use the new table for lookups) before we can start
+ * releasing the old bucket nodes. Otherwise their lookup will
+ * return a logically removed node as insert position.
+ */
+ ht->flavor->update_synchronize_rcu();
+ if (free_by_rcu_order)
+ cds_lfht_free_bucket_table(ht, free_by_rcu_order);
+
+ /*
+ * Set "removed" flag in bucket nodes about to be removed.
+ * Unlink all now-logically-removed bucket node pointers.
+ * Concurrent add/remove operation are helping us doing
+ * the gc.
+ */
+ remove_table(ht, i, len);
+
+ free_by_rcu_order = i;
+
+ dbg_printf("fini new size: %lu\n", 1UL << i);
+ if (CMM_LOAD_SHARED(ht->in_progress_destroy))
+ break;
+ }
+
+ if (free_by_rcu_order) {
+ ht->flavor->update_synchronize_rcu();
+ cds_lfht_free_bucket_table(ht, free_by_rcu_order);
+ }
+}
+
+static
+void cds_lfht_create_bucket(struct cds_lfht *ht, unsigned long size)
+{
+ struct cds_lfht_node *prev, *node;
+ unsigned long order, len, i;
+
+ cds_lfht_alloc_bucket_table(ht, 0);
+
+ dbg_printf("create bucket: order 0 index 0 hash 0\n");
+ node = bucket_at(ht, 0);
+ node->next = flag_bucket(get_end());
+ node->reverse_hash = 0;
+
+ for (order = 1; order < cds_lfht_get_count_order_ulong(size) + 1; order++) {
+ len = 1UL << (order - 1);
+ cds_lfht_alloc_bucket_table(ht, order);
+
+ for (i = 0; i < len; i++) {
+ /*
+ * Now, we are trying to init the node with the
+ * hash=(len+i) (which is also a bucket with the
+ * index=(len+i)) and insert it into the hash table,
+ * so this node has to be inserted after the bucket
+ * with the index=(len+i)&(len-1)=i. And because there
+ * is no other non-bucket node nor bucket node with
+ * larger index/hash inserted, so the bucket node
+ * being inserted should be inserted directly linked
+ * after the bucket node with index=i.
+ */
+ prev = bucket_at(ht, i);
+ node = bucket_at(ht, len + i);
+
+ dbg_printf("create bucket: order %lu index %lu hash %lu\n",
+ order, len + i, len + i);
+ node->reverse_hash = bit_reverse_ulong(len + i);
+
+ /* insert after prev */
+ assert(is_bucket(prev->next));
+ node->next = prev->next;
+ prev->next = flag_bucket(node);
+ }
+ }
+}
+
+struct cds_lfht *_cds_lfht_new(unsigned long init_size,
+ unsigned long min_nr_alloc_buckets,
+ unsigned long max_nr_buckets,
+ int flags,
+ const struct cds_lfht_mm_type *mm,
+ const struct rcu_flavor_struct *flavor,
+ pthread_attr_t *attr)
+{
+ struct cds_lfht *ht;
+ unsigned long order;
+
+ /* min_nr_alloc_buckets must be power of two */
+ if (!min_nr_alloc_buckets || (min_nr_alloc_buckets & (min_nr_alloc_buckets - 1)))
+ return NULL;
+
+ /* init_size must be power of two */
+ if (!init_size || (init_size & (init_size - 1)))
+ return NULL;
+
+ /*
+ * Memory management plugin default.
+ */
+ if (!mm) {
+ if (CAA_BITS_PER_LONG > 32
+ && max_nr_buckets
+ && max_nr_buckets <= (1ULL << 32)) {
+ /*
+ * For 64-bit architectures, with max number of
+ * buckets small enough not to use the entire
+ * 64-bit memory mapping space (and allowing a
+ * fair number of hash table instances), use the
+ * mmap allocator, which is faster than the
+ * order allocator.
+ */
+ mm = &cds_lfht_mm_mmap;
+ } else {
+ /*
+ * The fallback is to use the order allocator.
+ */
+ mm = &cds_lfht_mm_order;
+ }
+ }
+
+ /* max_nr_buckets == 0 for order based mm means infinite */
+ if (mm == &cds_lfht_mm_order && !max_nr_buckets)
+ max_nr_buckets = 1UL << (MAX_TABLE_ORDER - 1);
+
+ /* max_nr_buckets must be power of two */
+ if (!max_nr_buckets || (max_nr_buckets & (max_nr_buckets - 1)))
+ return NULL;
+
+ min_nr_alloc_buckets = max(min_nr_alloc_buckets, MIN_TABLE_SIZE);
+ init_size = max(init_size, MIN_TABLE_SIZE);
+ max_nr_buckets = max(max_nr_buckets, min_nr_alloc_buckets);
+ init_size = min(init_size, max_nr_buckets);
+
+ ht = mm->alloc_cds_lfht(min_nr_alloc_buckets, max_nr_buckets);
+ assert(ht);
+ assert(ht->mm == mm);
+ assert(ht->bucket_at == mm->bucket_at);
+
+ ht->flags = flags;
+ ht->flavor = flavor;
+ ht->resize_attr = attr;
+ alloc_split_items_count(ht);
+ /* this mutex should not nest in read-side C.S. */
+ pthread_mutex_init(&ht->resize_mutex, NULL);
+ order = cds_lfht_get_count_order_ulong(init_size);
+ ht->resize_target = 1UL << order;
+ cds_lfht_create_bucket(ht, 1UL << order);
+ ht->size = 1UL << order;
+ return ht;
+}
+
+void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
+ cds_lfht_match_fct match, const void *key,
+ struct cds_lfht_iter *iter)
+{
+ struct cds_lfht_node *node, *next, *bucket;
+ unsigned long reverse_hash, size;
+
+ reverse_hash = bit_reverse_ulong(hash);
+
+ size = rcu_dereference(ht->size);
+ bucket = lookup_bucket(ht, size, hash);
+ /* We can always skip the bucket node initially */
+ node = rcu_dereference(bucket->next);
+ node = clear_flag(node);
+ for (;;) {
+ if (caa_unlikely(is_end(node))) {
+ node = next = NULL;
+ break;
+ }
+ if (caa_unlikely(node->reverse_hash > reverse_hash)) {
+ node = next = NULL;
+ break;
+ }
+ next = rcu_dereference(node->next);
+ assert(node == clear_flag(node));
+ if (caa_likely(!is_removed(next))
+ && !is_bucket(next)
+ && node->reverse_hash == reverse_hash
+ && caa_likely(match(node, key))) {
+ break;
+ }
+ node = clear_flag(next);
+ }
+ assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
+ iter->node = node;
+ iter->next = next;
+}
+
+void cds_lfht_next_duplicate(struct cds_lfht *ht, cds_lfht_match_fct match,
+ const void *key, struct cds_lfht_iter *iter)
+{
+ struct cds_lfht_node *node, *next;
+ unsigned long reverse_hash;
+
+ node = iter->node;
+ reverse_hash = node->reverse_hash;
+ next = iter->next;
+ node = clear_flag(next);
+
+ for (;;) {
+ if (caa_unlikely(is_end(node))) {
+ node = next = NULL;
+ break;
+ }
+ if (caa_unlikely(node->reverse_hash > reverse_hash)) {
+ node = next = NULL;
+ break;
+ }
+ next = rcu_dereference(node->next);
+ if (caa_likely(!is_removed(next))
+ && !is_bucket(next)
+ && caa_likely(match(node, key))) {
+ break;
+ }
+ node = clear_flag(next);
+ }
+ assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
+ iter->node = node;
+ iter->next = next;
+}
+
+void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
+{
+ struct cds_lfht_node *node, *next;
+
+ node = clear_flag(iter->next);
+ for (;;) {
+ if (caa_unlikely(is_end(node))) {
+ node = next = NULL;
+ break;
+ }
+ next = rcu_dereference(node->next);
+ if (caa_likely(!is_removed(next))
+ && !is_bucket(next)) {
+ break;
+ }
+ node = clear_flag(next);
+ }
+ assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
+ iter->node = node;
+ iter->next = next;
+}
+
+void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter)
+{
+ /*
+ * Get next after first bucket node. The first bucket node is the
+ * first node of the linked list.
+ */
+ iter->next = bucket_at(ht, 0)->next;
+ cds_lfht_next(ht, iter);
+}
+
+void cds_lfht_add(struct cds_lfht *ht, unsigned long hash,
+ struct cds_lfht_node *node)
+{
+ unsigned long size;
+
+ node->reverse_hash = bit_reverse_ulong(hash);
+ size = rcu_dereference(ht->size);
+ _cds_lfht_add(ht, hash, NULL, NULL, size, node, NULL, 0);
+ ht_count_add(ht, size, hash);
+}
+
+struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
+ unsigned long hash,
+ cds_lfht_match_fct match,
+ const void *key,
+ struct cds_lfht_node *node)
+{
+ unsigned long size;
+ struct cds_lfht_iter iter;
+
+ node->reverse_hash = bit_reverse_ulong(hash);
+ size = rcu_dereference(ht->size);
+ _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
+ if (iter.node == node)
+ ht_count_add(ht, size, hash);
+ return iter.node;
+}
+
+struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
+ unsigned long hash,
+ cds_lfht_match_fct match,
+ const void *key,
+ struct cds_lfht_node *node)
+{
+ unsigned long size;
+ struct cds_lfht_iter iter;
+
+ node->reverse_hash = bit_reverse_ulong(hash);
+ size = rcu_dereference(ht->size);
+ for (;;) {
+ _cds_lfht_add(ht, hash, match, key, size, node, &iter, 0);
+ if (iter.node == node) {
+ ht_count_add(ht, size, hash);
+ return NULL;
+ }
+
+ if (!_cds_lfht_replace(ht, size, iter.node, iter.next, node))
+ return iter.node;
+ }
+}
+
+int cds_lfht_replace(struct cds_lfht *ht,
+ struct cds_lfht_iter *old_iter,
+ unsigned long hash,
+ cds_lfht_match_fct match,
+ const void *key,
+ struct cds_lfht_node *new_node)
+{
+ unsigned long size;
+
+ new_node->reverse_hash = bit_reverse_ulong(hash);
+ if (!old_iter->node)
+ return -ENOENT;
+ if (caa_unlikely(old_iter->node->reverse_hash != new_node->reverse_hash))
+ return -EINVAL;
+ if (caa_unlikely(!match(old_iter->node, key)))
+ return -EINVAL;
+ size = rcu_dereference(ht->size);
+ return _cds_lfht_replace(ht, size, old_iter->node, old_iter->next,
+ new_node);
+}
+
+int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
+{
+ unsigned long size;
+ int ret;
+
+ size = rcu_dereference(ht->size);
+ ret = _cds_lfht_del(ht, size, node);
+ if (!ret) {
+ unsigned long hash;
+
+ hash = bit_reverse_ulong(node->reverse_hash);
+ ht_count_del(ht, size, hash);
+ }
+ return ret;
+}
+
+int cds_lfht_is_node_deleted(struct cds_lfht_node *node)
+{
+ return is_removed(CMM_LOAD_SHARED(node->next));
+}
+
+static
+int cds_lfht_delete_bucket(struct cds_lfht *ht)
+{
+ struct cds_lfht_node *node;
+ unsigned long order, i, size;
+
+ /* Check that the table is empty */
+ node = bucket_at(ht, 0);
+ do {
+ node = clear_flag(node)->next;
+ if (!is_bucket(node))
+ return -EPERM;
+ assert(!is_removed(node));
+ } while (!is_end(node));
+ /*
+ * size accessed without rcu_dereference because hash table is
+ * being destroyed.
+ */
+ size = ht->size;
+ /* Internal sanity check: all nodes left should be buckets */
+ for (i = 0; i < size; i++) {
+ node = bucket_at(ht, i);
+ dbg_printf("delete bucket: index %lu expected hash %lu hash %lu\n",
+ i, i, bit_reverse_ulong(node->reverse_hash));
+ assert(is_bucket(node->next));
+ }
+
+ for (order = cds_lfht_get_count_order_ulong(size); (long)order >= 0; order--)
+ cds_lfht_free_bucket_table(ht, order);
+
+ return 0;
+}
+
+/*
+ * Should only be called when no more concurrent readers nor writers can
+ * possibly access the table.
+ */
+int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
+{
+ int ret;
+
+ /* Wait for in-flight resize operations to complete */
+ _CMM_STORE_SHARED(ht->in_progress_destroy, 1);
+ cmm_smp_mb(); /* Store destroy before load resize */
+ ht->flavor->thread_offline();
+ while (uatomic_read(&ht->in_progress_resize))
+ poll(NULL, 0, 100); /* wait for 100ms */
+ ht->flavor->thread_online();
+ ret = cds_lfht_delete_bucket(ht);
+ if (ret)
+ return ret;
+ free_split_items_count(ht);
+ if (attr)
+ *attr = ht->resize_attr;
+ poison_free(ht);
+ return ret;
+}
+
+void cds_lfht_count_nodes(struct cds_lfht *ht,
+ long *approx_before,
+ unsigned long *count,
+ long *approx_after)
+{
+ struct cds_lfht_node *node, *next;
+ unsigned long nr_bucket = 0, nr_removed = 0;
+
+ *approx_before = 0;
+ if (ht->split_count) {
+ int i;
+
+ for (i = 0; i < split_count_mask + 1; i++) {
+ *approx_before += uatomic_read(&ht->split_count[i].add);
+ *approx_before -= uatomic_read(&ht->split_count[i].del);
+ }
+ }
+
+ *count = 0;
+
+ /* Count non-bucket nodes in the table */
+ node = bucket_at(ht, 0);
+ do {
+ next = rcu_dereference(node->next);
+ if (is_removed(next)) {
+ if (!is_bucket(next))
+ (nr_removed)++;
+ else
+ (nr_bucket)++;
+ } else if (!is_bucket(next))
+ (*count)++;
+ else
+ (nr_bucket)++;
+ node = clear_flag(next);
+ } while (!is_end(node));
+ dbg_printf("number of logically removed nodes: %lu\n", nr_removed);
+ dbg_printf("number of bucket nodes: %lu\n", nr_bucket);
+ *approx_after = 0;
+ if (ht->split_count) {
+ int i;
+
+ for (i = 0; i < split_count_mask + 1; i++) {
+ *approx_after += uatomic_read(&ht->split_count[i].add);
+ *approx_after -= uatomic_read(&ht->split_count[i].del);
+ }
+ }
+}
+
+/* called with resize mutex held */
+static
+void _do_cds_lfht_grow(struct cds_lfht *ht,
+ unsigned long old_size, unsigned long new_size)
+{
+ unsigned long old_order, new_order;
+
+ old_order = cds_lfht_get_count_order_ulong(old_size);
+ new_order = cds_lfht_get_count_order_ulong(new_size);
+ dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
+ old_size, old_order, new_size, new_order);
+ assert(new_size > old_size);
+ init_table(ht, old_order + 1, new_order);
+}
+
+/* called with resize mutex held */
+static
+void _do_cds_lfht_shrink(struct cds_lfht *ht,
+ unsigned long old_size, unsigned long new_size)
+{
+ unsigned long old_order, new_order;
+
+ new_size = max(new_size, MIN_TABLE_SIZE);
+ old_order = cds_lfht_get_count_order_ulong(old_size);
+ new_order = cds_lfht_get_count_order_ulong(new_size);
+ dbg_printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
+ old_size, old_order, new_size, new_order);
+ assert(new_size < old_size);
+
+ /* Remove and unlink all bucket nodes to remove. */
+ fini_table(ht, new_order + 1, old_order);
+}
+
+
+/* called with resize mutex held */
+static
+void _do_cds_lfht_resize(struct cds_lfht *ht)
+{
+ unsigned long new_size, old_size;
+
+ /*
+ * Resize table, re-do if the target size has changed under us.
+ */
+ do {
+ assert(uatomic_read(&ht->in_progress_resize));
+ if (CMM_LOAD_SHARED(ht->in_progress_destroy))
+ break;
+ ht->resize_initiated = 1;
+ old_size = ht->size;
+ new_size = CMM_LOAD_SHARED(ht->resize_target);
+ if (old_size < new_size)
+ _do_cds_lfht_grow(ht, old_size, new_size);
+ else if (old_size > new_size)
+ _do_cds_lfht_shrink(ht, old_size, new_size);
+ ht->resize_initiated = 0;
+ /* write resize_initiated before read resize_target */
+ cmm_smp_mb();
+ } while (ht->size != CMM_LOAD_SHARED(ht->resize_target));
+}
+
+static
+unsigned long resize_target_grow(struct cds_lfht *ht, unsigned long new_size)
+{
+ return _uatomic_xchg_monotonic_increase(&ht->resize_target, new_size);
+}
+
+static
+void resize_target_update_count(struct cds_lfht *ht,
+ unsigned long count)
+{
+ count = max(count, MIN_TABLE_SIZE);
+ count = min(count, ht->max_nr_buckets);
+ uatomic_set(&ht->resize_target, count);
+}
+
+void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
+{
+ resize_target_update_count(ht, new_size);
+ CMM_STORE_SHARED(ht->resize_initiated, 1);
+ ht->flavor->thread_offline();
+ pthread_mutex_lock(&ht->resize_mutex);
+ _do_cds_lfht_resize(ht);
+ pthread_mutex_unlock(&ht->resize_mutex);
+ ht->flavor->thread_online();
+}
+
+static
+void do_resize_cb(struct rcu_head *head)
+{
+ struct rcu_resize_work *work =
+ caa_container_of(head, struct rcu_resize_work, head);
+ struct cds_lfht *ht = work->ht;
+
+ ht->flavor->thread_offline();
+ pthread_mutex_lock(&ht->resize_mutex);
+ _do_cds_lfht_resize(ht);
+ pthread_mutex_unlock(&ht->resize_mutex);
+ ht->flavor->thread_online();
+ poison_free(work);
+ cmm_smp_mb(); /* finish resize before decrement */
+ uatomic_dec(&ht->in_progress_resize);
+}
+
+static
+void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
+{
+ struct rcu_resize_work *work;
+
+ /* Store resize_target before read resize_initiated */
+ cmm_smp_mb();
+ if (!CMM_LOAD_SHARED(ht->resize_initiated)) {
+ uatomic_inc(&ht->in_progress_resize);
+ cmm_smp_mb(); /* increment resize count before load destroy */
+ if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
+ uatomic_dec(&ht->in_progress_resize);
+ return;
+ }
+ work = malloc(sizeof(*work));
+ if (work == NULL) {
+ dbg_printf("error allocating resize work, bailing out\n");
+ uatomic_dec(&ht->in_progress_resize);
+ return;
+ }
+ work->ht = ht;
+ ht->flavor->update_call_rcu(&work->head, do_resize_cb);
+ CMM_STORE_SHARED(ht->resize_initiated, 1);
+ }
+}
+
+static
+void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
+{
+ unsigned long target_size = size << growth;
+
+ target_size = min(target_size, ht->max_nr_buckets);
+ if (resize_target_grow(ht, target_size) >= target_size)
+ return;
+
+ __cds_lfht_resize_lazy_launch(ht);
+}
+
+/*
+ * We favor grow operations over shrink. A shrink operation never occurs
+ * if a grow operation is queued for lazy execution. A grow operation
+ * cancels any pending shrink lazy execution.
+ */
+static
+void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
+ unsigned long count)
+{
+ if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
+ return;
+ count = max(count, MIN_TABLE_SIZE);
+ count = min(count, ht->max_nr_buckets);
+ if (count == size)
+ return; /* Already the right size, no resize needed */
+ if (count > size) { /* lazy grow */
+ if (resize_target_grow(ht, count) >= count)
+ return;
+ } else { /* lazy shrink */
+ for (;;) {
+ unsigned long s;
+
+ s = uatomic_cmpxchg(&ht->resize_target, size, count);
+ if (s == size)
+ break; /* no resize needed */
+ if (s > size)
+ return; /* growing is/(was just) in progress */
+ if (s <= count)
+ return; /* some other thread do shrink */
+ size = s;
+ }
}
+ __cds_lfht_resize_lazy_launch(ht);
}
projects / urcu.git / blobdiff