Messages in this thread | | | Date | Wed, 11 May 2022 15:08:02 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] tools/perf: add breakpoint benchmarks |
| |
Em Wed, May 11, 2022 at 08:34:58AM -0700, Ian Rogers escreveu: > On Thu, May 5, 2022 at 8:58 AM Dmitry Vyukov <dvyukov@google.com> wrote: > > > > 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 > > > > Signed-off-by: Dmitry Vyukov <dvyukov@google.com> > > Acked-by: Ian Rogers <irogers@google.com>
Thanks, applied.
- Arnaldo
> > Cc: linux-perf-users@vger.kernel.org > > Cc: linux-kernel@vger.kernel.org > > --- > > tools/perf/bench/Build | 1 + > > tools/perf/bench/bench.h | 2 + > > tools/perf/bench/breakpoint.c | 235 ++++++++++++++++++++++++++++++++++ > > tools/perf/builtin-bench.c | 8 ++ > > 4 files changed, 246 insertions(+) > > create mode 100644 tools/perf/bench/breakpoint.c > > > > diff --git a/tools/perf/bench/Build b/tools/perf/bench/Build > > index 61d45fcb4057c..6b6155a8ad096 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 b3480bc33fe84..6cefb4315d75e 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 0000000000000..56936fea246d7 > > --- /dev/null > > +++ b/tools/perf/bench/breakpoint.c > > @@ -0,0 +1,235 @@ > > +// 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 = {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)) > > Note, this may be the first change with atomics since Linux moved to > C11 which may make the use of stdatomic.h more idiomatic. Just > flagging for potential future cleanup. > > Thanks, > Ian > > > + 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])); > > + 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])); > > + 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 <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])); > > + 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 d291f3a8af5f2..334ab897aae3b 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 } > > }; > > > > base-commit: bd24325684029a48f20a188b899eb84900d0bc9c > > -- > > 2.36.0.464.gb9c8b46e94-goog > >
--
- Arnaldo
| |