Commit a9be4f2c authored by Jim Harris's avatar Jim Harris Committed by Tomasz Zawadzki
Browse files

trace: add likely/unlikely hints to _spdk_trace_record 



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: default avatarJim Harris <james.r.harris@intel.com>
Change-Id: I7021b7f9e28b4a7cb16f8a97b4d4004ae165efd2
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/15096


Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarChangpeng Liu <changpeng.liu@intel.com>
Reviewed-by: default avatarKonrad Sztyber <konrad.sztyber@intel.com>
parent 4c6a2e3d

lib/trace/trace.c

+7 −5
Original line number Diff line number Diff line
@@ -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';

		}