From 68a6772f11dbb1ed8b74d4c8adc2da1f84dd32a6 Mon Sep 17 00:00:00 2001 From: Dmitry Vyukov Date: Thu, 5 May 2022 17:57:45 +0200 Subject: [PATCH] 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 Tested-by: Arnaldo Carvalho de Melo Acked-by: Ian Rogers Cc: Alexander Shishkin Cc: Ingo Molnar Cc: Jiri Olsa Cc: Marco Elver Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20220505155745.1690906-1-dvyukov@google.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/bench/Build | 1 + tools/perf/bench/bench.h | 2 + tools/perf/bench/breakpoint.c | 244 ++++++++++++++++++++++++++++++++++++++++++ tools/perf/builtin-bench.c | 8 ++ 4 files changed, 255 insertions(+) create mode 100644 tools/perf/bench/breakpoint.c diff --git a/tools/perf/bench/Build b/tools/perf/bench/Build index 61d45fc..6b6155a 100644 --- a/tools/perf/bench/Build +++ b/tools/perf/bench/Build @@ -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 diff --git a/tools/perf/bench/bench.h b/tools/perf/bench/bench.h index b3480bc..6cefb43 100644 --- a/tools/perf/bench/bench.h +++ b/tools/perf/bench/bench.h @@ -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 index 0000000..2f30a4d --- /dev/null +++ b/tools/perf/bench/breakpoint.c @@ -0,0 +1,244 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#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, }; + + 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(¶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 == -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; +} diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c index d291f3a..334ab89 100644 --- a/tools/perf/builtin-bench.c +++ b/tools/perf/builtin-bench.c @@ -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 } }; -- 2.7.4