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SubjectRe: [PATCH 1/9] perf/core: Add PERF_RECORD_CGROUP event
On Fri, Dec 20, 2019 at 01:32:45PM +0900, Namhyung Kim wrote:
> To support cgroup tracking, add CGROUP event to save a link between
> cgroup path and inode number. The attr.cgroup bit was also added to
> enable cgroup tracking from userspace.
>
> This event will be generated when a new cgroup becomes active.
> Userspace might need to synthesize those events for existing cgroups.
>
> 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>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

TJ, is this the right thing to do? ISTR you had concerns on this topic
on the past.

> ---
> include/uapi/linux/perf_event.h | 14 +++-
> kernel/events/core.c | 112 ++++++++++++++++++++++++++++++++
> 2 files changed, 125 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 377d794d3105..7bae2d3380a6 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -377,7 +377,8 @@ struct perf_event_attr {
> ksymbol : 1, /* include ksymbol events */
> bpf_event : 1, /* include bpf events */
> aux_output : 1, /* generate AUX records instead of events */
> - __reserved_1 : 32;
> + cgroup : 1, /* include cgroup events */
> + __reserved_1 : 31;
>
> union {
> __u32 wakeup_events; /* wakeup every n events */
> @@ -1006,6 +1007,17 @@ enum perf_event_type {
> */
> PERF_RECORD_BPF_EVENT = 18,
>
> + /*
> + * struct {
> + * struct perf_event_header header;
> + * u64 id;
> + * u64 path_len;

You can leave out path_len (also u64 for a length field is silly).

> + * char path[];
> + * struct sample_id sample_id;
> + * };
> + */
> + PERF_RECORD_CGROUP = 19,

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