Quelle  breakpoint.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0

#include <subcmd/parse-options.h>
#include <linux/hw_breakpoint.h>
#include <linux/perf_event.h>
#include <linux/time64.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <pthread.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include "bench.h"
#include "futex.h"

struct {
 unsigned int nbreakpoints;
 unsigned int nparallel;
 unsigned int nthreads;
} thread_params = {
 .nbreakpoints = 1,
 .nparallel = 1,
 .nthreads = 1,
};

static const struct option thread_options[] = {
 OPT_UINTEGER('b', "breakpoints", &thread_params.nbreakpoints,
  "Specify amount of breakpoints"),
 OPT_UINTEGER('p', "parallelism", &thread_params.nparallel, "Specify amount of parallelism"),
 OPT_UINTEGER('t', "threads", &thread_params.nthreads, "Specify amount of threads"),
 OPT_END()
};

static const char * const thread_usage[] = {
 "perf bench breakpoint thread ",
 NULL
};

struct breakpoint {
 int fd;
 char watched;
};

static int breakpoint_setup(void *addr)
{
 struct perf_event_attr attr = { .size = 0, };
 int fd;

 attr.type = PERF_TYPE_BREAKPOINT;
 attr.size = sizeof(attr);
 attr.inherit = 1;
 attr.exclude_kernel = 1;
 attr.exclude_hv = 1;
 attr.bp_addr = (unsigned long)addr;
 attr.bp_type = HW_BREAKPOINT_RW;
 attr.bp_len = HW_BREAKPOINT_LEN_1;
 fd = syscall(SYS_perf_event_open, &attr, 0, -1, -1, 0);

 if (fd < 0)
  fd = -errno;

 return fd;
}

static void *passive_thread(void *arg)
{
 unsigned int *done = (unsigned int *)arg;

 while (!__atomic_load_n(done, __ATOMIC_RELAXED))
  futex_wait(done, 0, NULL, 0);
 return NULL;
}

static void *active_thread(void *arg)
{
 unsigned int *done = (unsigned int *)arg;

 while (!__atomic_load_n(done, __ATOMIC_RELAXED));
 return NULL;
}

static void *breakpoint_thread(void *arg)
{
 unsigned int i, done;
 int *repeat = (int *)arg;
 pthread_t *threads;

 threads = calloc(thread_params.nthreads, sizeof(threads[0]));
 if (!threads)
  exit((perror("calloc"), EXIT_FAILURE));

 while (__atomic_fetch_sub(repeat, 1, __ATOMIC_RELAXED) > 0) {
  done = 0;
  for (i = 0; i < thread_params.nthreads; i++) {
   if (pthread_create(&threads[i], NULL, passive_thread, &done))
    exit((perror("pthread_create"), EXIT_FAILURE));
  }
  __atomic_store_n(&done, 1, __ATOMIC_RELAXED);
  futex_wake(&done, thread_params.nthreads, 0);
  for (i = 0; i < thread_params.nthreads; i++)
   pthread_join(threads[i], NULL);
 }
 free(threads);
 return NULL;
}

// The benchmark creates nbreakpoints inheritable breakpoints,
// then starts nparallel threads which create and join bench_repeat batches of nthreads threads.
int bench_breakpoint_thread(int argc, const char **argv)
{
 unsigned int i, result_usec;
 int repeat = bench_repeat;
 struct breakpoint *breakpoints;
 pthread_t *parallel;
 struct timeval start, stop, diff;

 if (parse_options(argc, argv, thread_options, thread_usage, 0)) {
  usage_with_options(thread_usage, thread_options);
  exit(EXIT_FAILURE);
 }
 breakpoints = calloc(thread_params.nbreakpoints, sizeof(breakpoints[0]));
 parallel = calloc(thread_params.nparallel, sizeof(parallel[0]));
 if (!breakpoints || !parallel)
  exit((perror("calloc"), EXIT_FAILURE));

 for (i = 0; i < thread_params.nbreakpoints; i++) {
  breakpoints[i].fd = breakpoint_setup(&breakpoints[i].watched);

  if (breakpoints[i].fd < 0) {
   if (breakpoints[i].fd == -ENODEV) {
    printf("Skipping perf bench breakpoint thread: No hardware support\n");
    return 0;
   }
   exit((perror("perf_event_open"), EXIT_FAILURE));
  }
 }
 gettimeofday(&start, NULL);
 for (i = 0; i < thread_params.nparallel; i++) {
  if (pthread_create(¶llel[i], NULL, breakpoint_thread, &repeat))
   exit((perror("pthread_create"), EXIT_FAILURE));
 }
 for (i = 0; i < thread_params.nparallel; i++)
  pthread_join(parallel[i], NULL);
 gettimeofday(&stop, NULL);
 timersub(&stop, &start, &diff);
 for (i = 0; i < thread_params.nbreakpoints; i++)
  close(breakpoints[i].fd);
 free(parallel);
 free(breakpoints);
 switch (bench_format) {
 case BENCH_FORMAT_DEFAULT:
  printf("# Created/joined %d threads with %d breakpoints and %d parallelism\n",
   bench_repeat, thread_params.nbreakpoints, thread_params.nparallel);
  printf(" %14s: %lu.%03lu [sec]\n\n", "Total time",
   (long)diff.tv_sec, (long)(diff.tv_usec / USEC_PER_MSEC));
  result_usec = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
  printf(" %14lf usecs/op\n",
   (double)result_usec / bench_repeat / thread_params.nthreads);
  printf(" %14lf usecs/op/cpu\n",
   (double)result_usec / bench_repeat /
   thread_params.nthreads * thread_params.nparallel);
  break;
 case BENCH_FORMAT_SIMPLE:
  printf("%lu.%03lu\n", (long)diff.tv_sec, (long)(diff.tv_usec / USEC_PER_MSEC));
  break;
 default:
  fprintf(stderr, "Unknown format: %d\n", bench_format);
  exit(EXIT_FAILURE);
 }
 return 0;
}

struct {
 unsigned int npassive;
 unsigned int nactive;
} enable_params = {
 .nactive = 0,
 .npassive = 0,
};

static const struct option enable_options[] = {
 OPT_UINTEGER('p', "passive", &enable_params.npassive, "Specify amount of passive threads"),
 OPT_UINTEGER('a', "active", &enable_params.nactive, "Specify amount of active threads"),
 OPT_END()
};

static const char * const enable_usage[] = {
 "perf bench breakpoint enable ",
 NULL
};

// The benchmark creates an inheritable breakpoint,
// then starts npassive threads that block and nactive threads that actively spin
// and then disables and enables the breakpoint bench_repeat times.
int bench_breakpoint_enable(int argc, const char **argv)
{
 unsigned int i, nthreads, result_usec, done = 0;
 char watched;
 int fd;
 pthread_t *threads;
 struct timeval start, stop, diff;

 if (parse_options(argc, argv, enable_options, enable_usage, 0)) {
  usage_with_options(enable_usage, enable_options);
  exit(EXIT_FAILURE);
 }
 fd = breakpoint_setup(&watched);

 if (fd < 0) {
  if (fd == -ENODEV) {
   printf("Skipping perf bench breakpoint enable: No hardware support\n");
   return 0;
  }
  exit((perror("perf_event_open"), EXIT_FAILURE));
 }
 nthreads = enable_params.npassive + enable_params.nactive;
 threads = calloc(nthreads, sizeof(threads[0]));
 if (!threads)
  exit((perror("calloc"), EXIT_FAILURE));

 for (i = 0; i < nthreads; i++) {
  if (pthread_create(&threads[i], NULL,
   i < enable_params.npassive ? passive_thread : active_thread, &done))
   exit((perror("pthread_create"), EXIT_FAILURE));
 }
 usleep(10000);  // let the threads block
 gettimeofday(&start, NULL);
 for (i = 0; i < bench_repeat; i++) {
  if (ioctl(fd, PERF_EVENT_IOC_DISABLE, 0))
   exit((perror("ioctl(PERF_EVENT_IOC_DISABLE)"), EXIT_FAILURE));
  if (ioctl(fd, PERF_EVENT_IOC_ENABLE, 0))
   exit((perror("ioctl(PERF_EVENT_IOC_ENABLE)"), EXIT_FAILURE));
 }
 gettimeofday(&stop, NULL);
 timersub(&stop, &start, &diff);
 __atomic_store_n(&done, 1, __ATOMIC_RELAXED);
 futex_wake(&done, enable_params.npassive, 0);
 for (i = 0; i < nthreads; i++)
  pthread_join(threads[i], NULL);
 free(threads);
 close(fd);
 switch (bench_format) {
 case BENCH_FORMAT_DEFAULT:
  printf("# Enabled/disabled breakpoint %d time with %d passive and %d active threads\n",
   bench_repeat, enable_params.npassive, enable_params.nactive);
  printf(" %14s: %lu.%03lu [sec]\n\n", "Total time",
   (long)diff.tv_sec, (long)(diff.tv_usec / USEC_PER_MSEC));
  result_usec = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
  printf(" %14lf usecs/op\n", (double)result_usec / bench_repeat);
  break;
 case BENCH_FORMAT_SIMPLE:
  printf("%lu.%03lu\n", (long)diff.tv_sec, (long)(diff.tv_usec / USEC_PER_MSEC));
  break;
 default:
  fprintf(stderr, "Unknown format: %d\n", bench_format);
  exit(EXIT_FAILURE);
 }
 return 0;
}