Quelle  pmu-scan.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0
/*
 * Benchmark scanning sysfs files for PMU information.
 *
 * Copyright 2023 Google LLC.
 */
#include <stdio.h>
#include "bench.h"
#include "util/debug.h"
#include "util/pmu.h"
#include "util/pmus.h"
#include "util/stat.h"
#include <linux/atomic.h>
#include <linux/err.h>
#include <linux/time64.h>
#include <subcmd/parse-options.h>

static unsigned int iterations = 100;

struct pmu_scan_result {
 char *name;
 int nr_aliases;
 int nr_formats;
 int nr_caps;
 bool is_core;
};

static const struct option options[] = {
 OPT_UINTEGER('i', "iterations", &iterations,
  "Number of iterations used to compute average"),
 OPT_END()
};

static const char *const bench_usage[] = {
 "perf bench internals pmu-scan ",
 NULL
};

static int nr_pmus;
static struct pmu_scan_result *results;

static int save_result(void)
{
 struct perf_pmu *pmu = NULL;
 struct list_head *list;
 struct pmu_scan_result *r;

 while ((pmu = perf_pmus__scan(pmu)) != NULL) {
  r = realloc(results, (nr_pmus + 1) * sizeof(*r));
  if (r == NULL)
   return -ENOMEM;

  results = r;
  r = results + nr_pmus;

  r->name = strdup(pmu->name);
  r->is_core = pmu->is_core;
  r->nr_caps = pmu->nr_caps;

  r->nr_aliases = perf_pmu__num_events(pmu);

  r->nr_formats = 0;
  list_for_each(list, &pmu->format)
   r->nr_formats++;

  pr_debug("pmu[%d] name=%s, nr_caps=%d, nr_aliases=%d, nr_formats=%d\n",
   nr_pmus, r->name, r->nr_caps, r->nr_aliases, r->nr_formats);
  nr_pmus++;
 }

 perf_pmus__destroy();
 return 0;
}

static int check_result(bool core_only)
{
 struct pmu_scan_result *r;
 struct perf_pmu *pmu;
 struct list_head *list;
 int nr;

 for (int i = 0; i < nr_pmus; i++) {
  r = &results[i];
  if (core_only && !r->is_core)
   continue;

  pmu = perf_pmus__find(r->name);
  if (pmu == NULL) {
   pr_err("Cannot find PMU %s\n", r->name);
   return -1;
  }

  if (pmu->nr_caps != (u32)r->nr_caps) {
   pr_err("Unmatched number of event caps in %s: expect %d vs got %d\n",
    pmu->name, r->nr_caps, pmu->nr_caps);
   return -1;
  }

  nr = perf_pmu__num_events(pmu);
  if (nr != r->nr_aliases) {
   pr_err("Unmatched number of event aliases in %s: expect %d vs got %d\n",
    pmu->name, r->nr_aliases, nr);
   return -1;
  }

  nr = 0;
  list_for_each(list, &pmu->format)
   nr++;
  if (nr != r->nr_formats) {
   pr_err("Unmatched number of event formats in %s: expect %d vs got %d\n",
    pmu->name, r->nr_formats, nr);
   return -1;
  }
 }
 return 0;
}

static void delete_result(void)
{
 for (int i = 0; i < nr_pmus; i++)
  free(results[i].name);
 free(results);

 results = NULL;
 nr_pmus = 0;
}

static int run_pmu_scan(void)
{
 struct stats stats;
 struct timeval start, end, diff;
 double time_average, time_stddev;
 u64 runtime_us;
 int ret;

 init_stats(&stats);
 pr_info("Computing performance of sysfs PMU event scan for %u times\n",
  iterations);

 if (save_result() < 0) {
  pr_err("Failed to initialize PMU scan result\n");
  return -1;
 }

 for (int j = 0; j < 2; j++) {
  bool core_only = (j == 0);

  for (unsigned int i = 0; i < iterations; i++) {
   gettimeofday(&start, NULL);
   if (core_only)
    perf_pmus__scan_core(NULL);
   else
    perf_pmus__scan(NULL);
   gettimeofday(&end, NULL);
   timersub(&end, &start, &diff);
   runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
   update_stats(&stats, runtime_us);

   ret = check_result(core_only);
   perf_pmus__destroy();
   if (ret < 0)
    break;
  }
  time_average = avg_stats(&stats);
  time_stddev = stddev_stats(&stats);
  pr_info(" Average%s PMU scanning took: %.3f usec (+- %.3f usec)\n",
   core_only ? " core" : "", time_average, time_stddev);
 }
 delete_result();
 return 0;
}

int bench_pmu_scan(int argc, const char **argv)
{
 int err = 0;

 argc = parse_options(argc, argv, options, bench_usage, 0);
 if (argc) {
  usage_with_options(bench_usage, options);
  exit(EXIT_FAILURE);
 }

 err = run_pmu_scan();

 return err;
}