perf bench: Add breakpoint benchmarks
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>
This commit is contained in:
Dmitry Vyukov
Arnaldo Carvalho de Melo
parent
467cd948f8
commit
68a6772f11
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@ -14,6 +14,7 @@ perf-y += kallsyms-parse.o
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perf-y += find-bit-bench.o
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perf-y += inject-buildid.o
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perf-y += evlist-open-close.o
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perf-y += breakpoint.o
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perf-$(CONFIG_X86_64) += mem-memcpy-x86-64-asm.o
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perf-$(CONFIG_X86_64) += mem-memset-x86-64-asm.o
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@ -49,6 +49,8 @@ int bench_synthesize(int argc, const char **argv);
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int bench_kallsyms_parse(int argc, const char **argv);
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int bench_inject_build_id(int argc, const char **argv);
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int bench_evlist_open_close(int argc, const char **argv);
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int bench_breakpoint_thread(int argc, const char **argv);
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int bench_breakpoint_enable(int argc, const char **argv);
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#define BENCH_FORMAT_DEFAULT_STR "default"
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#define BENCH_FORMAT_DEFAULT 0
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@ -0,0 +1,244 @@
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// SPDX-License-Identifier: GPL-2.0
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#include <subcmd/parse-options.h>
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#include <linux/hw_breakpoint.h>
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#include <linux/perf_event.h>
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#include <linux/time64.h>
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#include <sys/syscall.h>
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#include <sys/ioctl.h>
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#include <sys/time.h>
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#include <pthread.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <errno.h>
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#include "bench.h"
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#include "futex.h"
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struct {
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unsigned int nbreakpoints;
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unsigned int nparallel;
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unsigned int nthreads;
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} thread_params = {
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.nbreakpoints = 1,
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.nparallel = 1,
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.nthreads = 1,
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};
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static const struct option thread_options[] = {
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OPT_UINTEGER('b', "breakpoints", &thread_params.nbreakpoints,
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"Specify amount of breakpoints"),
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OPT_UINTEGER('p', "parallelism", &thread_params.nparallel, "Specify amount of parallelism"),
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OPT_UINTEGER('t', "threads", &thread_params.nthreads, "Specify amount of threads"),
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OPT_END()
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};
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static const char * const thread_usage[] = {
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"perf bench breakpoint thread <options>",
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NULL
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};
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struct breakpoint {
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int fd;
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char watched;
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};
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static int breakpoint_setup(void *addr)
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{
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struct perf_event_attr attr = { .size = 0, };
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attr.type = PERF_TYPE_BREAKPOINT;
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attr.size = sizeof(attr);
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attr.inherit = 1;
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attr.exclude_kernel = 1;
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attr.exclude_hv = 1;
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attr.bp_addr = (uint64_t)addr;
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attr.bp_type = HW_BREAKPOINT_RW;
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attr.bp_len = HW_BREAKPOINT_LEN_1;
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return syscall(SYS_perf_event_open, &attr, 0, -1, -1, 0);
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}
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static void *passive_thread(void *arg)
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{
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unsigned int *done = (unsigned int *)arg;
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while (!__atomic_load_n(done, __ATOMIC_RELAXED))
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futex_wait(done, 0, NULL, 0);
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return NULL;
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}
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static void *active_thread(void *arg)
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{
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unsigned int *done = (unsigned int *)arg;
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while (!__atomic_load_n(done, __ATOMIC_RELAXED));
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return NULL;
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}
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static void *breakpoint_thread(void *arg)
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{
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unsigned int i, done;
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int *repeat = (int *)arg;
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pthread_t *threads;
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threads = calloc(thread_params.nthreads, sizeof(threads[0]));
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if (!threads)
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exit((perror("calloc"), EXIT_FAILURE));
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while (__atomic_fetch_sub(repeat, 1, __ATOMIC_RELAXED) > 0) {
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done = 0;
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for (i = 0; i < thread_params.nthreads; i++) {
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if (pthread_create(&threads[i], NULL, passive_thread, &done))
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exit((perror("pthread_create"), EXIT_FAILURE));
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}
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__atomic_store_n(&done, 1, __ATOMIC_RELAXED);
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futex_wake(&done, thread_params.nthreads, 0);
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for (i = 0; i < thread_params.nthreads; i++)
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pthread_join(threads[i], NULL);
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}
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free(threads);
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return NULL;
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}
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// The benchmark creates nbreakpoints inheritable breakpoints,
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// then starts nparallel threads which create and join bench_repeat batches of nthreads threads.
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int bench_breakpoint_thread(int argc, const char **argv)
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{
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unsigned int i, result_usec;
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int repeat = bench_repeat;
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struct breakpoint *breakpoints;
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pthread_t *parallel;
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struct timeval start, stop, diff;
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if (parse_options(argc, argv, thread_options, thread_usage, 0)) {
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usage_with_options(thread_usage, thread_options);
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exit(EXIT_FAILURE);
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}
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breakpoints = calloc(thread_params.nbreakpoints, sizeof(breakpoints[0]));
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parallel = calloc(thread_params.nparallel, sizeof(parallel[0]));
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if (!breakpoints || !parallel)
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exit((perror("calloc"), EXIT_FAILURE));
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for (i = 0; i < thread_params.nbreakpoints; i++) {
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breakpoints[i].fd = breakpoint_setup(&breakpoints[i].watched);
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if (breakpoints[i].fd == -1)
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exit((perror("perf_event_open"), EXIT_FAILURE));
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}
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gettimeofday(&start, NULL);
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for (i = 0; i < thread_params.nparallel; i++) {
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if (pthread_create(¶llel[i], NULL, breakpoint_thread, &repeat))
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exit((perror("pthread_create"), EXIT_FAILURE));
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}
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for (i = 0; i < thread_params.nparallel; i++)
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pthread_join(parallel[i], NULL);
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gettimeofday(&stop, NULL);
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timersub(&stop, &start, &diff);
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for (i = 0; i < thread_params.nbreakpoints; i++)
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close(breakpoints[i].fd);
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free(parallel);
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free(breakpoints);
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switch (bench_format) {
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case BENCH_FORMAT_DEFAULT:
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printf("# Created/joined %d threads with %d breakpoints and %d parallelism\n",
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bench_repeat, thread_params.nbreakpoints, thread_params.nparallel);
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printf(" %14s: %lu.%03lu [sec]\n\n", "Total time",
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(long)diff.tv_sec, (long)(diff.tv_usec / USEC_PER_MSEC));
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result_usec = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
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printf(" %14lf usecs/op\n",
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(double)result_usec / bench_repeat / thread_params.nthreads);
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printf(" %14lf usecs/op/cpu\n",
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(double)result_usec / bench_repeat /
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thread_params.nthreads * thread_params.nparallel);
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break;
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case BENCH_FORMAT_SIMPLE:
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printf("%lu.%03lu\n", (long)diff.tv_sec, (long)(diff.tv_usec / USEC_PER_MSEC));
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break;
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default:
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fprintf(stderr, "Unknown format: %d\n", bench_format);
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exit(EXIT_FAILURE);
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}
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return 0;
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}
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struct {
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unsigned int npassive;
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unsigned int nactive;
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} enable_params = {
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.nactive = 0,
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.npassive = 0,
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};
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static const struct option enable_options[] = {
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OPT_UINTEGER('p', "passive", &enable_params.npassive, "Specify amount of passive threads"),
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OPT_UINTEGER('a', "active", &enable_params.nactive, "Specify amount of active threads"),
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OPT_END()
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};
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static const char * const enable_usage[] = {
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"perf bench breakpoint enable <options>",
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NULL
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};
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// The benchmark creates an inheritable breakpoint,
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// then starts npassive threads that block and nactive threads that actively spin
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// and then disables and enables the breakpoint bench_repeat times.
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int bench_breakpoint_enable(int argc, const char **argv)
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{
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unsigned int i, nthreads, result_usec, done = 0;
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char watched;
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int fd;
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pthread_t *threads;
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struct timeval start, stop, diff;
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if (parse_options(argc, argv, enable_options, enable_usage, 0)) {
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usage_with_options(enable_usage, enable_options);
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exit(EXIT_FAILURE);
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}
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fd = breakpoint_setup(&watched);
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if (fd == -1)
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exit((perror("perf_event_open"), EXIT_FAILURE));
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nthreads = enable_params.npassive + enable_params.nactive;
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threads = calloc(nthreads, sizeof(threads[0]));
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if (!threads)
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exit((perror("calloc"), EXIT_FAILURE));
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for (i = 0; i < nthreads; i++) {
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if (pthread_create(&threads[i], NULL,
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i < enable_params.npassive ? passive_thread : active_thread, &done))
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exit((perror("pthread_create"), EXIT_FAILURE));
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}
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usleep(10000); // let the threads block
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gettimeofday(&start, NULL);
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for (i = 0; i < bench_repeat; i++) {
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if (ioctl(fd, PERF_EVENT_IOC_DISABLE, 0))
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exit((perror("ioctl(PERF_EVENT_IOC_DISABLE)"), EXIT_FAILURE));
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if (ioctl(fd, PERF_EVENT_IOC_ENABLE, 0))
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exit((perror("ioctl(PERF_EVENT_IOC_ENABLE)"), EXIT_FAILURE));
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}
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gettimeofday(&stop, NULL);
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timersub(&stop, &start, &diff);
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__atomic_store_n(&done, 1, __ATOMIC_RELAXED);
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futex_wake(&done, enable_params.npassive, 0);
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for (i = 0; i < nthreads; i++)
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pthread_join(threads[i], NULL);
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free(threads);
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close(fd);
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switch (bench_format) {
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case BENCH_FORMAT_DEFAULT:
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printf("# Enabled/disabled breakpoint %d time with %d passive and %d active threads\n",
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bench_repeat, enable_params.npassive, enable_params.nactive);
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printf(" %14s: %lu.%03lu [sec]\n\n", "Total time",
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(long)diff.tv_sec, (long)(diff.tv_usec / USEC_PER_MSEC));
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result_usec = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
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printf(" %14lf usecs/op\n", (double)result_usec / bench_repeat);
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break;
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case BENCH_FORMAT_SIMPLE:
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printf("%lu.%03lu\n", (long)diff.tv_sec, (long)(diff.tv_usec / USEC_PER_MSEC));
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break;
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default:
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fprintf(stderr, "Unknown format: %d\n", bench_format);
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exit(EXIT_FAILURE);
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}
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return 0;
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}
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@ -92,6 +92,13 @@ static struct bench internals_benchmarks[] = {
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{ NULL, NULL, NULL }
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};
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static struct bench breakpoint_benchmarks[] = {
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{ "thread", "Benchmark thread start/finish with breakpoints", bench_breakpoint_thread},
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{ "enable", "Benchmark breakpoint enable/disable", bench_breakpoint_enable},
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{ "all", "Run all breakpoint benchmarks", NULL},
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{ NULL, NULL, NULL },
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};
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struct collection {
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const char *name;
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const char *summary;
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@ -110,6 +117,7 @@ static struct collection collections[] = {
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{"epoll", "Epoll stressing benchmarks", epoll_benchmarks },
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#endif
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{ "internals", "Perf-internals benchmarks", internals_benchmarks },
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{ "breakpoint", "Breakpoint benchmarks", breakpoint_benchmarks },
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{ "all", "All benchmarks", NULL },
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{ NULL, NULL, NULL }
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};
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