Messages in this thread | | | From | Namhyung Kim <> | Date | Sat, 21 Dec 2019 17:49:02 +0900 | Subject | Re: [PATCH 1/9] perf/core: Add PERF_RECORD_CGROUP event |
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Hi Tejun,
On Sat, Dec 21, 2019 at 12:16 AM Tejun Heo <tj@kernel.org> wrote: > > On Fri, Dec 20, 2019 at 10:33:35AM +0100, Peter Zijlstra wrote: > > 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. > > Yeah, cgroup->id is now the same as ino (on 64bit ino matchines) and > fhandle and uniquely identifies a cgroup instance in that boot > instance. That said, id -> path mapping can be done from userspace by > passing the cgroup id to open_by_handle_at(2) and then reading the > symlink in /proc/self/fd, so this event isn't necessary per-se if the > goal is mapping back ids to paths.
But we should support offline report even on a different machine. Also cgroups might go away during the record. so I think we need it anyway.
Thanks Namhyung
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