X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=include%2Fringbuffer%2Fconfig.h;h=df7c335d9c6bbf27254938cc19e39e510dbd0a59;hb=refs%2Ftags%2Ffor-upstreaming-review-1;hp=e1f0a9656281ad14286af28f523048035b41198f;hpb=369708f464bedc0682151df9308cebfa14dbdb2b;p=lttng-modules.git diff --git a/include/ringbuffer/config.h b/include/ringbuffer/config.h index e1f0a965..df7c335d 100644 --- a/include/ringbuffer/config.h +++ b/include/ringbuffer/config.h @@ -1,2 +1,306 @@ -/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) */ -#include +/* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only) + * + * lib/ringbuffer/config.h + * + * Ring buffer configuration header. Note: after declaring the standard inline + * functions, clients should also include linux/ringbuffer/api.h. + * + * Copyright (C) 2010-2012 Mathieu Desnoyers + */ + +#ifndef _LIB_RING_BUFFER_CONFIG_H +#define _LIB_RING_BUFFER_CONFIG_H + +#include +#include +#include +#include + +struct lib_ring_buffer; +struct channel; +struct lib_ring_buffer_config; +struct lib_ring_buffer_ctx; + +/* + * Ring buffer client callbacks. Only used by slow path, never on fast path. + * For the fast path, record_header_size(), ring_buffer_clock_read() should be + * provided as inline functions too. These may simply return 0 if not used by + * the client. + */ +struct lib_ring_buffer_client_cb { + /* Mandatory callbacks */ + + /* A static inline version is also required for fast path */ + u64 (*ring_buffer_clock_read) (struct channel *chan); + size_t (*record_header_size) (const struct lib_ring_buffer_config *config, + struct channel *chan, size_t offset, + size_t *pre_header_padding, + struct lib_ring_buffer_ctx *ctx, + void *client_ctx); + + /* Slow path only, at subbuffer switch */ + size_t (*subbuffer_header_size) (void); + void (*buffer_begin) (struct lib_ring_buffer *buf, u64 tsc, + unsigned int subbuf_idx); + void (*buffer_end) (struct lib_ring_buffer *buf, u64 tsc, + unsigned int subbuf_idx, unsigned long data_size); + + /* Optional callbacks (can be set to NULL) */ + + /* Called at buffer creation/finalize */ + int (*buffer_create) (struct lib_ring_buffer *buf, void *priv, + int cpu, const char *name); + /* + * Clients should guarantee that no new reader handle can be opened + * after finalize. + */ + void (*buffer_finalize) (struct lib_ring_buffer *buf, void *priv, int cpu); + + /* + * Extract header length, payload length and timestamp from event + * record. Used by buffer iterators. Timestamp is only used by channel + * iterator. + */ + void (*record_get) (const struct lib_ring_buffer_config *config, + struct channel *chan, struct lib_ring_buffer *buf, + size_t offset, size_t *header_len, + size_t *payload_len, u64 *timestamp); +}; + +/* + * Ring buffer instance configuration. + * + * Declare as "static const" within the client object to ensure the inline fast + * paths can be optimized. + * + * alloc/sync pairs: + * + * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_PER_CPU : + * Per-cpu buffers with per-cpu synchronization. Tracing must be performed + * with preemption disabled (lib_ring_buffer_get_cpu() and + * lib_ring_buffer_put_cpu()). + * + * RING_BUFFER_ALLOC_PER_CPU and RING_BUFFER_SYNC_GLOBAL : + * Per-cpu buffer with global synchronization. Tracing can be performed with + * preemption enabled, statistically stays on the local buffers. + * + * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_PER_CPU : + * Should only be used for buffers belonging to a single thread or protected + * by mutual exclusion by the client. Note that periodical sub-buffer switch + * should be disabled in this kind of configuration. + * + * RING_BUFFER_ALLOC_GLOBAL and RING_BUFFER_SYNC_GLOBAL : + * Global shared buffer with global synchronization. + * + * wakeup: + * + * RING_BUFFER_WAKEUP_BY_TIMER uses per-cpu timers to poll the + * buffers and wake up readers if data is ready. Mainly useful for tracers which + * don't want to call into the wakeup code on the tracing path. Use in + * combination with "read_timer_interval" channel_create() argument. + * + * RING_BUFFER_WAKEUP_BY_WRITER directly wakes up readers when a subbuffer is + * ready to read. Lower latencies before the reader is woken up. Mainly suitable + * for drivers. + * + * RING_BUFFER_WAKEUP_NONE does not perform any wakeup whatsoever. The client + * has the responsibility to perform wakeups. + */ +struct lib_ring_buffer_config { + enum { + RING_BUFFER_ALLOC_PER_CPU, + RING_BUFFER_ALLOC_GLOBAL, + } alloc; + enum { + RING_BUFFER_SYNC_PER_CPU, /* Wait-free */ + RING_BUFFER_SYNC_GLOBAL, /* Lock-free */ + } sync; + enum { + RING_BUFFER_OVERWRITE, /* Overwrite when buffer full */ + RING_BUFFER_DISCARD, /* Discard when buffer full */ + } mode; + enum { + RING_BUFFER_SPLICE, + RING_BUFFER_MMAP, + RING_BUFFER_READ, /* TODO */ + RING_BUFFER_ITERATOR, + RING_BUFFER_NONE, + } output; + enum { + RING_BUFFER_PAGE, + RING_BUFFER_VMAP, /* TODO */ + RING_BUFFER_STATIC, /* TODO */ + } backend; + enum { + RING_BUFFER_NO_OOPS_CONSISTENCY, + RING_BUFFER_OOPS_CONSISTENCY, + } oops; + enum { + RING_BUFFER_IPI_BARRIER, + RING_BUFFER_NO_IPI_BARRIER, + } ipi; + enum { + RING_BUFFER_WAKEUP_BY_TIMER, /* wake up performed by timer */ + RING_BUFFER_WAKEUP_BY_WRITER, /* + * writer wakes up reader, + * not lock-free + * (takes spinlock). + */ + } wakeup; + /* + * tsc_bits: timestamp bits saved at each record. + * 0 and 64 disable the timestamp compression scheme. + */ + unsigned int tsc_bits; + struct lib_ring_buffer_client_cb cb; +}; + +/* + * ring buffer context + * + * Context passed to lib_ring_buffer_reserve(), lib_ring_buffer_commit(), + * lib_ring_buffer_try_discard_reserve(), lib_ring_buffer_align_ctx() and + * lib_ring_buffer_write(). + */ +struct lib_ring_buffer_ctx { + /* input received by lib_ring_buffer_reserve(), saved here. */ + struct channel *chan; /* channel */ + void *priv; /* client private data */ + size_t data_size; /* size of payload */ + int largest_align; /* + * alignment of the largest element + * in the payload + */ + int cpu; /* processor id */ + + /* output from lib_ring_buffer_reserve() */ + struct lib_ring_buffer *buf; /* + * buffer corresponding to processor id + * for this channel + */ + size_t slot_size; /* size of the reserved slot */ + unsigned long buf_offset; /* offset following the record header */ + unsigned long pre_offset; /* + * Initial offset position _before_ + * the record is written. Positioned + * prior to record header alignment + * padding. + */ + u64 tsc; /* time-stamp counter value */ + unsigned int rflags; /* reservation flags */ + /* Cache backend pages pointer chasing. */ + struct lib_ring_buffer_backend_pages *backend_pages; +}; + +/** + * lib_ring_buffer_ctx_init - initialize ring buffer context + * @ctx: ring buffer context to initialize + * @chan: channel + * @priv: client private data + * @data_size: size of record data payload. It must be greater than 0. + * @largest_align: largest alignment within data payload types + * @cpu: processor id + */ +static inline +void lib_ring_buffer_ctx_init(struct lib_ring_buffer_ctx *ctx, + struct channel *chan, void *priv, + size_t data_size, int largest_align, + int cpu) +{ + ctx->chan = chan; + ctx->priv = priv; + ctx->data_size = data_size; + ctx->largest_align = largest_align; + ctx->cpu = cpu; + ctx->rflags = 0; + ctx->backend_pages = NULL; +} + +/* + * Reservation flags. + * + * RING_BUFFER_RFLAG_FULL_TSC + * + * This flag is passed to record_header_size() and to the primitive used to + * write the record header. It indicates that the full 64-bit time value is + * needed in the record header. If this flag is not set, the record header needs + * only to contain "tsc_bits" bit of time value. + * + * Reservation flags can be added by the client, starting from + * "(RING_BUFFER_FLAGS_END << 0)". It can be used to pass information from + * record_header_size() to lib_ring_buffer_write_record_header(). + */ +#define RING_BUFFER_RFLAG_FULL_TSC (1U << 0) +#define RING_BUFFER_RFLAG_END (1U << 1) + +#ifndef LTTNG_TRACER_CORE_H +#error "lttng-tracer-core.h is needed for RING_BUFFER_ALIGN define" +#endif + +/* + * We need to define RING_BUFFER_ALIGN_ATTR so it is known early at + * compile-time. We have to duplicate the "config->align" information and the + * definition here because config->align is used both in the slow and fast + * paths, but RING_BUFFER_ALIGN_ATTR is only available for the client code. + */ +#ifdef RING_BUFFER_ALIGN + +# define RING_BUFFER_ALIGN_ATTR /* Default arch alignment */ + +/* + * Calculate the offset needed to align the type. + * size_of_type must be non-zero. + */ +static inline +unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type) +{ + return offset_align(align_drift, size_of_type); +} + +#else + +# define RING_BUFFER_ALIGN_ATTR __attribute__((packed)) + +/* + * Calculate the offset needed to align the type. + * size_of_type must be non-zero. + */ +static inline +unsigned int lib_ring_buffer_align(size_t align_drift, size_t size_of_type) +{ + return 0; +} + +#endif + +/** + * lib_ring_buffer_align_ctx - Align context offset on "alignment" + * @ctx: ring buffer context. + */ +static inline +void lib_ring_buffer_align_ctx(struct lib_ring_buffer_ctx *ctx, + size_t alignment) +{ + ctx->buf_offset += lib_ring_buffer_align(ctx->buf_offset, + alignment); +} + +/* + * lib_ring_buffer_check_config() returns 0 on success. + * Used internally to check for valid configurations at channel creation. + */ +static inline +int lib_ring_buffer_check_config(const struct lib_ring_buffer_config *config, + unsigned int switch_timer_interval, + unsigned int read_timer_interval) +{ + if (config->alloc == RING_BUFFER_ALLOC_GLOBAL + && config->sync == RING_BUFFER_SYNC_PER_CPU + && switch_timer_interval) + return -EINVAL; + return 0; +} + +#include + +#endif /* _LIB_RING_BUFFER_CONFIG_H */