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trace: add likely/unlikely hints to _spdk_trace_record

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This helps generate slightly better code in this function,
which can have a noticeable impact for high trace
event workloads.

Tested with bdevperf, single malloc or null bdev,
qd=32, 512B randreads on a single Xeon core.
Specify "-e bdev" to enable bdev trace events.

Null:
Before: 8.09M/s (123ns per IO)
After: 8.68M/s (115ns per IO)

Malloc:
Before: 4.21M/s (237ns per IO)
After: 4.34M/s (230ns per IO)

Note that each bdev I/O generates two trace events (START
and END) - meaning this change removes 7-8ns of overhead
for every 2 trace events, at least on my system.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: I7021b7f9e28b4a7cb16f8a97b4d4004ae165efd2
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/15096
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Konrad Sztyber <konrad.sztyber@intel.com>
This commit is contained in:
Jim Harris 2022-10-20 13:38:46 -07:00 committed by Tomasz Zawadzki
parent 4c6a2e3daa
commit a9be4f2c2f
1 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
lib/trace/trace.c
View File

@ -12,6 +12,7 @@
#include "spdk/barrier.h"
#include "spdk/log.h"
#include "spdk/cpuset.h"
#include "spdk/likely.h"
static int g_trace_fd = -1;
static char g_shm_name[64];
@ -39,11 +40,12 @@ _spdk_trace_record(uint64_t tsc, uint16_t tpoint_id, uint16_t poller_id, uint32_
va_list vl;
lcore = spdk_env_get_current_core();
if (lcore >= SPDK_TRACE_MAX_LCORE) {
if (spdk_unlikely(lcore >= SPDK_TRACE_MAX_LCORE)) {
return;
}
lcore_history = spdk_get_per_lcore_history(g_trace_histories, lcore);
if (tsc == 0) {
tsc = spdk_get_ticks();
}
@ -52,7 +54,7 @@ _spdk_trace_record(uint64_t tsc, uint16_t tpoint_id, uint16_t poller_id, uint32_
tpoint = &g_trace_flags->tpoint[tpoint_id];
/* Make sure that the number of arguments passed matches tracepoint definition */
if (tpoint->num_args != num_args) {
if (spdk_unlikely(tpoint->num_args != num_args)) {
assert(0 && "Unexpected number of tracepoint arguments");
return;
}
@ -106,7 +108,7 @@ _spdk_trace_record(uint64_t tsc, uint16_t tpoint_id, uint16_t poller_id, uint32_
argoff = 0;
while (argoff < argument->size) {
/* Current buffer is full, we need to acquire another one */
if (offset == sizeof(buffer->data)) {
if (spdk_unlikely(offset == sizeof(buffer->data))) {
buffer = (struct spdk_trace_entry_buffer *) get_trace_entry(
lcore_history,
lcore_history->next_entry + num_entries);
@ -117,7 +119,7 @@ _spdk_trace_record(uint64_t tsc, uint16_t tpoint_id, uint16_t poller_id, uint32_
}
curlen = spdk_min(sizeof(buffer->data) - offset, argument->size - argoff);
if (argoff < arglen) {
if (spdk_likely(argoff < arglen)) {
assert(argval != NULL);
memcpy(&buffer->data[offset], (uint8_t *)argval + argoff,
spdk_min(curlen, arglen - argoff));
@ -128,7 +130,7 @@ _spdk_trace_record(uint64_t tsc, uint16_t tpoint_id, uint16_t poller_id, uint32_
}
/* Make sure that truncated strings are NULL-terminated */
if (argument->type == SPDK_TRACE_ARG_TYPE_STR) {
if (spdk_unlikely(argument->type == SPDK_TRACE_ARG_TYPE_STR)) {
assert(offset > 0);
buffer->data[offset - 1] = '\0';
}