Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3] perf bench sched pipe: Add -G/--cgroups option | From | Athira Rajeev <> | Date | Mon, 16 Oct 2023 22:55:22 +0530 |
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> On 16-Oct-2023, at 10:12 AM, Namhyung Kim <namhyung@kernel.org> wrote: > > The -G/--cgroups option is to put sender and receiver in different > cgroups in order to measure cgroup context switch overheads. > > Users need to make sure the cgroups exist and accessible. > > # perf stat -e context-switches,cgroup-switches \ >> taskset -c 0 perf bench sched pipe -l 10000 > /dev/null > > Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000': > > 20,001 context-switches > 2 cgroup-switches > > 0.053449651 seconds time elapsed > > 0.011286000 seconds user > 0.041869000 seconds sys > > # perf stat -e context-switches,cgroup-switches \ >> taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB > /dev/null > > Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB': > > 20,001 context-switches > 20,001 cgroup-switches > > 0.052768627 seconds time elapsed > > 0.006284000 seconds user > 0.046266000 seconds sys > > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Hi Namhyung,
I tried V3 on top of perf-tools-next
# ./perf stat -e context-switches,cgroup-switches taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB > /dev/null no access to cgroup /sys/fs/cgroup/perf_event/AAA cannot open sender cgroup: AAA Usage: perf bench sched pipe <options>
-G, --cgroups <SEND,RECV> Put sender and receivers in given cgroups
Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB':
2 context-switches 0 cgroup-switches
0.007291460 seconds time elapsed
0.007438000 seconds user 0.000000000 seconds sys
I created AAA and BBB mkdir /sys/fs/cgroup/perf_event/AAA mkdir /sys/fs/cgroup/perf_event/BBB
Got the results below:
./perf stat -e context-switches,cgroup-switches taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB > /dev/null
Performance counter stats for 'taskset -c 0 perf bench sched pipe -l 10000 -G AAA,BBB':
20002 context-switches 19999 cgroup-switches
0.120063986 seconds time elapsed
0.001716000 seconds user 0.065995000 seconds sys
Thanks Athira
> --- > tools/perf/Documentation/perf-bench.txt | 19 ++++ > tools/perf/bench/sched-pipe.c | 118 +++++++++++++++++++++++- > 2 files changed, 134 insertions(+), 3 deletions(-) > > diff --git a/tools/perf/Documentation/perf-bench.txt b/tools/perf/Documentation/perf-bench.txt > index ca5789625cd2..8331bd28b10e 100644 > --- a/tools/perf/Documentation/perf-bench.txt > +++ b/tools/perf/Documentation/perf-bench.txt > @@ -124,6 +124,14 @@ Options of *pipe* > --loop=:: > Specify number of loops. > > +-G:: > +--cgroups=:: > +Names of cgroups for sender and receiver, separated by a comma. > +This is useful to check cgroup context switching overhead. > +Note that perf doesn't create nor delete the cgroups, so users should > +make sure that the cgroups exist and are accessible before use. > + > + > Example of *pipe* > ^^^^^^^^^^^^^^^^^ > > @@ -141,6 +149,17 @@ Example of *pipe* > Total time:0.016 sec > 16.948000 usecs/op > 59004 ops/sec > + > +% perf bench sched pipe -G AAA,BBB > +(executing 1000000 pipe operations between cgroups) > +# Running 'sched/pipe' benchmark: > +# Executed 1000000 pipe operations between two processes > + > + Total time: 6.886 [sec] > + > + 6.886208 usecs/op > + 145217 ops/sec > + > --------------------- > > SUITES FOR 'syscall' > diff --git a/tools/perf/bench/sched-pipe.c b/tools/perf/bench/sched-pipe.c > index a960e7a93aec..88d20a34adb2 100644 > --- a/tools/perf/bench/sched-pipe.c > +++ b/tools/perf/bench/sched-pipe.c > @@ -10,7 +10,9 @@ > * Ported to perf by Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> > */ > #include <subcmd/parse-options.h> > +#include <api/fs/fs.h> > #include "bench.h" > +#include "util/cgroup.h" > > #include <unistd.h> > #include <stdio.h> > @@ -19,6 +21,7 @@ > #include <sys/wait.h> > #include <string.h> > #include <errno.h> > +#include <fcntl.h> > #include <assert.h> > #include <sys/time.h> > #include <sys/types.h> > @@ -31,6 +34,7 @@ struct thread_data { > int nr; > int pipe_read; > int pipe_write; > + bool cgroup_failed; > pthread_t pthread; > }; > > @@ -40,9 +44,55 @@ static int loops = LOOPS_DEFAULT; > /* Use processes by default: */ > static bool threaded; > > +static struct cgroup *cgrp_send = NULL; > +static struct cgroup *cgrp_recv = NULL; > + > +static int parse_two_cgroups(const struct option *opt __maybe_unused, > + const char *str, int unset __maybe_unused) > +{ > + char *p = strdup(str); > + char *q; > + int ret = -1; > + > + if (p == NULL) { > + fprintf(stderr, "memory allocation failure"); > + return -1; > + } > + > + q = strchr(p, ','); > + if (q == NULL) { > + fprintf(stderr, "it should have two cgroup names: %s", p); > + goto out; > + } > + *q = '\0'; > + > + cgrp_send = cgroup__new(p, /*do_open=*/true); > + if (cgrp_send == NULL) { > + fprintf(stderr, "cannot open sender cgroup: %s", p); > + goto out; > + } > + > + /* skip ',' */ > + q++; > + > + cgrp_recv = cgroup__new(q, /*do_open=*/true); > + if (cgrp_recv == NULL) { > + fprintf(stderr, "cannot open receiver cgroup: %s", q); > + goto out; > + } > + ret = 0; > + > +out: > + free(p); > + return ret; > +} > + > static const struct option options[] = { > OPT_INTEGER('l', "loop", &loops, "Specify number of loops"), > OPT_BOOLEAN('T', "threaded", &threaded, "Specify threads/process based task setup"), > + OPT_CALLBACK('G', "cgroups", NULL, "SEND,RECV", > + "Put sender and receivers in given cgroups", > + parse_two_cgroups), > OPT_END() > }; > > @@ -51,12 +101,71 @@ static const char * const bench_sched_pipe_usage[] = { > NULL > }; > > +static int enter_cgroup(struct cgroup *cgrp) > +{ > + char buf[32]; > + int fd, len, ret; > + pid_t pid; > + > + if (cgrp == NULL) > + return 0; > + > + if (threaded) > + pid = syscall(__NR_gettid); > + else > + pid = getpid(); > + > + snprintf(buf, sizeof(buf), "%d\n", pid); > + len = strlen(buf); > + > + /* try cgroup v2 interface first */ > + if (threaded) > + fd = openat(cgrp->fd, "cgroup.threads", O_WRONLY); > + else > + fd = openat(cgrp->fd, "cgroup.procs", O_WRONLY); > + > + /* try cgroup v1 if failed */ > + if (fd < 0) > + fd = openat(cgrp->fd, "tasks", O_WRONLY); > + > + if (fd < 0) { > + char mnt[PATH_MAX]; > + > + printf("Failed to open cgroup file in %s\n", cgrp->name); > + > + if (cgroupfs_find_mountpoint(mnt, sizeof(mnt), "perf_event") == 0) > + printf(" Hint: create the cgroup first, like 'mkdir %s/%s'\n", > + mnt, cgrp->name); > + return -1; > + } > + > + ret = write(fd, buf, len); > + close(fd); > + > + if (ret != len) { > + printf("Cannot enter to cgroup: %s\n", cgrp->name); > + return -1; > + } > + return 0; > +} > + > static void *worker_thread(void *__tdata) > { > struct thread_data *td = __tdata; > int m = 0, i; > int ret; > > + if (td->nr) > + ret = enter_cgroup(cgrp_send); > + else > + ret = enter_cgroup(cgrp_recv); > + > + if (ret < 0) { > + td->cgroup_failed = true; > + return NULL; > + } > + td->cgroup_failed = false; > + > for (i = 0; i < loops; i++) { > if (!td->nr) { > ret = read(td->pipe_read, &m, sizeof(int)); > @@ -112,9 +221,7 @@ int bench_sched_pipe(int argc, const char **argv) > } > } > > - > if (threaded) { > - > for (t = 0; t < nr_threads; t++) { > td = threads + t; > > @@ -128,7 +235,6 @@ int bench_sched_pipe(int argc, const char **argv) > ret = pthread_join(td->pthread, NULL); > BUG_ON(ret); > } > - > } else { > pid = fork(); > assert(pid >= 0); > @@ -147,6 +253,12 @@ int bench_sched_pipe(int argc, const char **argv) > gettimeofday(&stop, NULL); > timersub(&stop, &start, &diff); > > + cgroup__put(cgrp_send); > + cgroup__put(cgrp_recv); > + > + if (threads[0].cgroup_failed || threads[1].cgroup_failed) > + return 0; > + > switch (bench_format) { > case BENCH_FORMAT_DEFAULT: > printf("# Executed %d pipe operations between two %s\n\n", > -- > 2.42.0.655.g421f12c284-goog >
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