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SubjectRe: [PATCHSET 00/10] perf: Improve cgroup profiling (v5)
Hello Peter, Tejun and folks.

Do you have any other comments on the kernel side?
If not, can I get your Ack?

Thanks
Namhyung


On Mon, Feb 24, 2020 at 1:37 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hello,
>
> This work is to improve cgroup profiling in perf. Currently it only
> supports profiling tasks in a specific cgroup and there's no way to
> identify which cgroup the current sample belongs to. So I added
> PERF_SAMPLE_CGROUP to add cgroup id into each sample. It's a 64-bit
> integer having file handle of the cgroup. And kernel also generates
> PERF_RECORD_CGROUP event for new groups to correlate the cgroup id and
> cgroup name (path in the cgroup filesystem). The cgroup id can be
> read from userspace by name_to_handle_at() system call so it can
> synthesize the CGROUP event for existing groups.
>
> So why do we want this? Systems running a large number of jobs in
> different cgroups want to profiling such jobs precisely. This includes
> container hosting systems widely used today. Currently perf supports
> namespace tracking but the systems may not use (cgroup) namespace for
> their jobs. Also it'd be more intuitive to see cgroup names (as
> they're given by user or sysadmin) rather than numeric
> cgroup/namespace id even if they use the namespaces.
>
> From Stephane Eranian:
> > In data centers you care about attributing samples to a job not such
> > much to a process. A job may have multiple processes which may come
> > and go. The cgroup on the other hand stays around for the entire
> > lifetime of the job. It is much easier to map a cgroup name to a
> > particular job than it is to map a pid back to a job name,
> > especially for offline post-processing.
>
> Note that this only works for "perf_event" cgroups (obviously) so if
> users are still using cgroup-v1 interface, they need to have same
> hierarchy for subsystem(s) want to profile with it.
>
> * Changes from v4:
> - use CONFIG_CGROUP_PERF
> - move cgroup tree to perf_env
> - move cgroup fs utility function to tools/lib/api/fs
> - use a local buffer and check its size for cgroup systhesis
>
> * Changes from v3:
> - staticize perf_event_cgroup()
> - fix sample parsing test
>
> * Changes from v2:
> - remove path_len from cgroup_event
> - bail out if kernel doesn't support cgroup sampling
> - add some description in the Kconfig
>
> * Changes from v1:
> - use new cgroup id (= file handle)
>
> The code is available at perf/cgroup-v5 branch in
>
> git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
>
>
> The testing result looks something like this:
>
> [root@qemu build]# ./perf record --all-cgroups ./cgtest
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.009 MB perf.data (150 samples) ]
>
> [root@qemu build]# ./perf report -s cgroup,comm --stdio
> # To display the perf.data header info, please use --header/--header-only options.
> #
> #
> # Total Lost Samples: 0
> #
> # Samples: 150 of event 'cpu-clock:pppH'
> # Event count (approx.): 37500000
> #
> # Overhead cgroup Command
> # ........ .......... .......
> #
> 32.00% /sub/cgrp2 looper2
> 28.00% /sub/cgrp1 looper1
> 25.33% /sub looper0
> 4.00% / cgtest
> 4.00% /sub cgtest
> 3.33% /sub/cgrp2 cgtest
> 2.67% /sub/cgrp1 cgtest
> 0.67% / looper0
>
>
> The test program (cgtest) follows.
>
> Thanks,
> Namhyung
>
>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Li Zefan <lizefan@huawei.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
>
>
> -------8<-----------------------------------------8<----------------
> #define _GNU_SOURCE
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <unistd.h>
> #include <fcntl.h>
> #include <sched.h>
> #include <errno.h>
> #include <sys/stat.h>
> #include <sys/wait.h>
> #include <sys/prctl.h>
> #include <sys/mount.h>
>
> char cgbase[] = "/sys/fs/cgroup/perf_event";
>
> void mkcgrp(char *name) {
> char buf[256];
>
> snprintf(buf, sizeof(buf), "%s%s", cgbase, name);
> if (mkdir(buf, 0755) < 0)
> perror("mkdir");
> }
>
> void rmcgrp(char *name) {
> char buf[256];
>
> snprintf(buf, sizeof(buf), "%s%s", cgbase, name);
> if (rmdir(buf) < 0)
> perror("rmdir");
> }
>
> void setcgrp(char *name) {
> char buf[256];
> int fd;
>
> snprintf(buf, sizeof(buf), "%s%s/tasks", cgbase, name);
>
> fd = open(buf, O_WRONLY);
> if (fd > 0) {
> if (write(fd, "0\n", 2) != 2)
> perror("write");
> close(fd);
> }
> }
>
> void create_sub_cgroup(int idx) {
> char buf[128];
>
> snprintf(buf, sizeof(buf), "/sub/cgrp%d", idx);
> mkcgrp(buf);
> }
>
> void remove_sub_cgroup(int idx) {
> char buf[128];
>
> snprintf(buf, sizeof(buf), "/sub/cgrp%d", idx);
> rmcgrp(buf);
> }
>
> void set_sub_cgroup(int idx) {
> char buf[128];
>
> snprintf(buf, sizeof(buf), "/sub/cgrp%d", idx);
> setcgrp(buf);
> }
>
> void set_task_name(int idx) {
> char buf[16];
>
> snprintf(buf, sizeof(buf), "looper%d", idx);
> prctl(PR_SET_NAME, buf, 0, 0, 0);
> }
>
> void loop(unsigned max) {
> volatile unsigned int count = 1;
>
> while (count++ != max) {
> asm volatile ("pause");
> }
> }
>
> void worker(int idx, unsigned cnt, int new_ns) {
> int oldns;
>
> create_sub_cgroup(idx);
> set_sub_cgroup(idx);
>
> if (new_ns) {
> if (unshare(CLONE_NEWCGROUP) < 0)
> perror("unshare");
>
> #if 0 /* FIXME */
> if (unshare(CLONE_NEWNS) < 0)
> perror("unshare");
>
> if (mount("none", "/sys", NULL, MS_REMOUNT | MS_REC | MS_SLAVE, NULL) < 0)
> perror("mount --make-rslave");
>
> sleep(1);
> if (umount("/sys/fs/cgroup/perf_event") < 0)
> perror("umount");
>
> if (mount("cgroup", "/sys/fs/cgroup/perf_event", "cgroup",
> MS_NODEV | MS_NOEXEC | MS_NOSUID, "perf_event") < 0)
> perror("mount again");
> #endif
> }
>
> if (fork() == 0) {
> set_task_name(idx);
> loop(cnt);
> exit(0);
> }
> wait(NULL);
> }
>
> int main(int argc, char *argv[])
> {
> int i, nr = 2;
> int new_ns = 1;
> unsigned cnt = 1000000;
> int fd;
>
> if (argc > 1)
> nr = atoi(argv[1]);
> if (argc > 2)
> cnt = atoi(argv[2]);
> if (argc > 3)
> new_ns = atoi(argv[3]);
>
> mkcgrp("/sub");
> setcgrp("/sub");
>
> for (i = 0; i < nr; i++) {
> if (fork() == 0) {
> worker(i+1, cnt, new_ns);
> exit(0);
> }
> }
>
> set_task_name(0);
> loop(cnt);
>
> for (i = 0; i < nr; i++)
> wait(NULL);
>
> for (i = 0; i < nr; i++)
> remove_sub_cgroup(i+1);
>
> setcgrp("/");
> rmcgrp("/sub");
>
> return 0;
> }
> -------8<-----------------------------------------8<----------------
>
>
> Namhyung Kim (10):
> perf/core: Add PERF_RECORD_CGROUP event
> perf/core: Add PERF_SAMPLE_CGROUP feature
> tools lib api fs: Move cgroupsfs__mountpoint()
> perf tools: Basic support for CGROUP event
> perf tools: Maintain cgroup hierarchy
> perf report: Add 'cgroup' sort key
> perf record: Support synthesizing cgroup events
> perf record: Add --all-cgroups option
> perf top: Add --all-cgroups option
> perf script: Add --show-cgroup-events option
>
> include/linux/perf_event.h | 1 +
> include/uapi/linux/perf_event.h | 16 ++-
> init/Kconfig | 3 +-
> kernel/events/core.c | 133 ++++++++++++++++++++
> tools/include/uapi/linux/perf_event.h | 16 ++-
> tools/lib/api/fs/Build | 1 +
> tools/lib/api/fs/cgroup.c | 67 ++++++++++
> tools/lib/api/fs/fs.h | 2 +
> tools/lib/perf/include/perf/event.h | 7 ++
> tools/perf/Documentation/perf-record.txt | 5 +-
> tools/perf/Documentation/perf-report.txt | 1 +
> tools/perf/Documentation/perf-script.txt | 3 +
> tools/perf/Documentation/perf-top.txt | 4 +
> tools/perf/builtin-diff.c | 1 +
> tools/perf/builtin-record.c | 10 ++
> tools/perf/builtin-report.c | 1 +
> tools/perf/builtin-script.c | 41 +++++++
> tools/perf/builtin-top.c | 9 ++
> tools/perf/tests/sample-parsing.c | 6 +-
> tools/perf/util/cgroup.c | 143 +++++++++++++---------
> tools/perf/util/cgroup.h | 18 ++-
> tools/perf/util/env.c | 2 +
> tools/perf/util/env.h | 6 +
> tools/perf/util/event.c | 19 +++
> tools/perf/util/event.h | 6 +
> tools/perf/util/evsel.c | 17 ++-
> tools/perf/util/evsel.h | 1 +
> tools/perf/util/hist.c | 12 ++
> tools/perf/util/hist.h | 1 +
> tools/perf/util/machine.c | 19 +++
> tools/perf/util/machine.h | 3 +
> tools/perf/util/perf_event_attr_fprintf.c | 2 +
> tools/perf/util/record.h | 1 +
> tools/perf/util/session.c | 4 +
> tools/perf/util/sort.c | 37 ++++++
> tools/perf/util/sort.h | 2 +
> tools/perf/util/synthetic-events.c | 121 ++++++++++++++++++
> tools/perf/util/synthetic-events.h | 1 +
> tools/perf/util/tool.h | 2 +
> 39 files changed, 671 insertions(+), 73 deletions(-)
> create mode 100644 tools/lib/api/fs/cgroup.c
>
> --
> 2.25.0.265.gbab2e86ba0-goog
>

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