perf bench: Add breakpoint benchmarks
authorDmitry Vyukov <dvyukov@google.com>
Thu, 5 May 2022 15:57:45 +0000 (17:57 +0200)
committerArnaldo Carvalho de Melo <acme@redhat.com>
Fri, 13 May 2022 14:00:38 +0000 (11:00 -0300)
Add 2 benchmarks:

1. Performance of thread creation/exiting in presence of breakpoints.
2. Performance of breakpoint modification in presence of threads.

The benchmarks capture use cases that we are interested in:
using inheritable breakpoints in large highly-threaded applications.

The benchmarks show significant slowdown imposed by breakpoints
(even when they don't fire).

Testing on Intel 8173M with 112 HW threads show:

  perf bench --repeat=56 breakpoint thread --breakpoints=0 --parallelism=56 --threads=20
        78.675000 usecs/op
  perf bench --repeat=56 breakpoint thread --breakpoints=4 --parallelism=56 --threads=20
     12967.135714 usecs/op

That's 165x slowdown due to presence of the breakpoints.

  perf bench --repeat=20000 breakpoint enable --passive=0 --active=0
         1.433250 usecs/op
  perf bench --repeat=20000 breakpoint enable --passive=224 --active=0
       585.318400 usecs/op
  perf bench --repeat=20000 breakpoint enable --passive=0 --active=111
       635.953000 usecs/op

That's 408x and 444x slowdown due to presence of threads.

Profiles show some overhead in toggle_bp_slot,
but also very high contention:

    90.83%  breakpoint-thre  [kernel.kallsyms]  [k] osq_lock
     4.69%  breakpoint-thre  [kernel.kallsyms]  [k] mutex_spin_on_owner
     2.06%  breakpoint-thre  [kernel.kallsyms]  [k] __reserve_bp_slot
     2.04%  breakpoint-thre  [kernel.kallsyms]  [k] toggle_bp_slot

    79.01%  breakpoint-enab  [kernel.kallsyms]  [k] smp_call_function_single
     9.94%  breakpoint-enab  [kernel.kallsyms]  [k] llist_add_batch
     5.70%  breakpoint-enab  [kernel.kallsyms]  [k] _raw_spin_lock_irq
     1.84%  breakpoint-enab  [kernel.kallsyms]  [k] event_function_call
     1.12%  breakpoint-enab  [kernel.kallsyms]  [k] send_call_function_single_ipi
     0.37%  breakpoint-enab  [kernel.kallsyms]  [k] generic_exec_single
     0.24%  breakpoint-enab  [kernel.kallsyms]  [k] __perf_event_disable
     0.20%  breakpoint-enab  [kernel.kallsyms]  [k] _perf_event_enable
     0.18%  breakpoint-enab  [kernel.kallsyms]  [k] toggle_bp_slot

Committer notes:

Fixup struct init for older compilers:

   3    32.90 alpine:3.5                    : FAIL clang version 3.8.1 (tags/RELEASE_381/final)
    bench/breakpoint.c:49:34: error: missing field 'size' initializer [-Werror,-Wmissing-field-initializers]
            struct perf_event_attr attr = {0};
                                            ^
    1 error generated.
   7    37.31 alpine:3.9                    : FAIL gcc version 8.3.0 (Alpine 8.3.0)
    bench/breakpoint.c:49:34: error: missing field 'size' initializer [-Werror,-Wmissing-field-initializers]
            struct perf_event_attr attr = {0};
                                            ^
    1 error generated.

Signed-off-by: Dmitriy Vyukov <dvyukov@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220505155745.1690906-1-dvyukov@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
tools/perf/bench/Build
tools/perf/bench/bench.h
tools/perf/bench/breakpoint.c [new file with mode: 0644]
tools/perf/builtin-bench.c

index 61d45fc..6b6155a 100644 (file)
@@ -14,6 +14,7 @@ perf-y += kallsyms-parse.o
 perf-y += find-bit-bench.o
 perf-y += inject-buildid.o
 perf-y += evlist-open-close.o
+perf-y += breakpoint.o
 
 perf-$(CONFIG_X86_64) += mem-memcpy-x86-64-asm.o
 perf-$(CONFIG_X86_64) += mem-memset-x86-64-asm.o
index b3480bc..6cefb43 100644 (file)
@@ -49,6 +49,8 @@ int bench_synthesize(int argc, const char **argv);
 int bench_kallsyms_parse(int argc, const char **argv);
 int bench_inject_build_id(int argc, const char **argv);
 int bench_evlist_open_close(int argc, const char **argv);
+int bench_breakpoint_thread(int argc, const char **argv);
+int bench_breakpoint_enable(int argc, const char **argv);
 
 #define BENCH_FORMAT_DEFAULT_STR       "default"
 #define BENCH_FORMAT_DEFAULT           0
diff --git a/tools/perf/bench/breakpoint.c b/tools/perf/bench/breakpoint.c
new file mode 100644 (file)
index 0000000..2f30a4d
--- /dev/null
@@ -0,0 +1,244 @@
+// 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 <options>",
+       NULL
+};
+
+struct breakpoint {
+       int fd;
+       char watched;
+};
+
+static int breakpoint_setup(void *addr)
+{
+       struct perf_event_attr attr = { .size = 0, };
+
+       attr.type = PERF_TYPE_BREAKPOINT;
+       attr.size = sizeof(attr);
+       attr.inherit = 1;
+       attr.exclude_kernel = 1;
+       attr.exclude_hv = 1;
+       attr.bp_addr = (uint64_t)addr;
+       attr.bp_type = HW_BREAKPOINT_RW;
+       attr.bp_len = HW_BREAKPOINT_LEN_1;
+       return syscall(SYS_perf_event_open, &attr, 0, -1, -1, 0);
+}
+
+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 == -1)
+                       exit((perror("perf_event_open"), EXIT_FAILURE));
+       }
+       gettimeofday(&start, NULL);
+       for (i = 0; i < thread_params.nparallel; i++) {
+               if (pthread_create(&parallel[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 <options>",
+       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 == -1)
+               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;
+}
index d291f3a..334ab89 100644 (file)
@@ -92,6 +92,13 @@ static struct bench internals_benchmarks[] = {
        { NULL,         NULL,                                   NULL                    }
 };
 
+static struct bench breakpoint_benchmarks[] = {
+       { "thread", "Benchmark thread start/finish with breakpoints", bench_breakpoint_thread},
+       { "enable", "Benchmark breakpoint enable/disable", bench_breakpoint_enable},
+       { "all", "Run all breakpoint benchmarks", NULL},
+       { NULL, NULL, NULL },
+};
+
 struct collection {
        const char      *name;
        const char      *summary;
@@ -110,6 +117,7 @@ static struct collection collections[] = {
        {"epoll",       "Epoll stressing benchmarks",                   epoll_benchmarks        },
 #endif
        { "internals",  "Perf-internals benchmarks",                    internals_benchmarks    },
+       { "breakpoint", "Breakpoint benchmarks",                        breakpoint_benchmarks   },
        { "all",        "All benchmarks",                               NULL                    },
        { NULL,         NULL,                                           NULL                    }
 };