Performance: Only dereference shmp once

[lttng-ust.git] / libringbuffer / frontend_api.h

diff --git a/libringbuffer/frontend_api.h b/libringbuffer/frontend_api.h
index 77a269184fcf1f3dbc26380f7e2e201cd25bd497..eea2a8db579686995d1c204995fdb4dcda51668b 100644 (file)
--- a/libringbuffer/frontend_api.h
+++ b/libringbuffer/frontend_api.h
@@ -60,7 +60,6 @@ int lib_ring_buffer_get_cpu(const struct lttng_ust_lib_ring_buffer_config *confi
        if (caa_unlikely(nesting > 4)) {
                WARN_ON_ONCE(1);
                URCU_TLS(lib_ring_buffer_nesting)--;
-               rcu_read_unlock();
                return -EPERM;
        } else
                return cpu;
@@ -161,14 +160,14 @@ int lib_ring_buffer_reserve(const struct lttng_ust_lib_ring_buffer_config *confi
        unsigned long o_begin, o_end, o_old;
        size_t before_hdr_pad = 0;
 
-       if (uatomic_read(&chan->record_disabled))
+       if (caa_unlikely(uatomic_read(&chan->record_disabled)))
                return -EAGAIN;
 
        if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
                buf = shmp(handle, chan->backend.buf[ctx->cpu].shmp);
        else
                buf = shmp(handle, chan->backend.buf[0].shmp);
-       if (uatomic_read(&buf->record_disabled))
+       if (caa_unlikely(uatomic_read(&buf->record_disabled)))
                return -EAGAIN;
        ctx->buf = buf;
 
@@ -251,6 +250,8 @@ void lib_ring_buffer_commit(const struct lttng_ust_lib_ring_buffer_config *confi
        unsigned long offset_end = ctx->buf_offset;
        unsigned long endidx = subbuf_index(offset_end - 1, chan);
        unsigned long commit_count;
+       struct commit_counters_hot *cc_hot = shmp_index(handle,
+                                               buf->commit_hot, endidx);
 
        /*
         * Must count record before incrementing the commit count.
@@ -263,7 +264,7 @@ void lib_ring_buffer_commit(const struct lttng_ust_lib_ring_buffer_config *confi
         */
        cmm_smp_wmb();
 
-       v_add(config, ctx->slot_size, &shmp_index(handle, buf->commit_hot, endidx)->cc);
+       v_add(config, ctx->slot_size, &cc_hot->cc);
 
        /*
         * commit count read can race with concurrent OOO commit count updates.
@@ -283,7 +284,7 @@ void lib_ring_buffer_commit(const struct lttng_ust_lib_ring_buffer_config *confi
         *   count reaches back the reserve offset for a specific sub-buffer,
         *   which is completely independent of the order.
         */
-       commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, endidx)->cc);
+       commit_count = v_read(config, &cc_hot->cc);
 
        lib_ring_buffer_check_deliver(config, buf, chan, offset_end - 1,
                                      commit_count, endidx, handle, ctx->tsc);
@@ -291,8 +292,8 @@ void lib_ring_buffer_commit(const struct lttng_ust_lib_ring_buffer_config *confi
         * Update used size at each commit. It's needed only for extracting
         * ring_buffer buffers from vmcore, after crash.
         */
-       lib_ring_buffer_write_commit_counter(config, buf, chan, endidx,
-                       offset_end, commit_count, handle);
+       lib_ring_buffer_write_commit_counter(config, buf, chan,
+                       offset_end, commit_count, handle, cc_hot);
 }
 
 /**