* l...@cn.fujitsu.com <l...@cn.fujitsu.com> [2010-11-26 09:50:24]:
> 19:28, Peter Zijlstra wrote:
> > On Thu, 2010-11-18 at 12:40 +0200, Stephane Eranian wrote:
> >> This kernel patch adds the ability to filter monitoring based on
> >> container groups (cgroups). This is for use in per-cpu mode only.
> >>
> >> The cgroup to monitor is passed as a file descriptor in the pid
> >> argument to the syscall. The file descriptor must be opened to
> >> the cgroup name in the cgroup filesystem. For instance, if the
> >> cgroup name is foo and cgroupfs is mounted in /cgroup, then the
> >> file descriptor is opened to /cgroup/foo. Cgroup mode is
> >> activated by passing PERF_FLAG_PID_CGROUP in the flags argument
> >> to the syscall.
> >>
> >> For instance to measure in cgroup foo on CPU1 assuming
> >> cgroupfs is mounted under /cgroup:
> >>
> >> struct perf_event_attr attr;
> >> int cgroup_fd, fd;
> >>
> >> cgroup_fd = open("/cgroup/foo", O_RDONLY);
> >> fd = perf_event_open(&attr, cgroup_fd, 1, -1, PERF_FLAG_PID_CGROUP);
> >> close(cgroup_fd);
> >>
> >> Signed-off-by: Stephane Eranian <eran...@google.com>
> >
> > Could you please split this patch:
> > - pure code movement
> > - time accounting changes
> > - event_filter_match() stuff
> > - cgroup thing
> >
> > From a quick reading it doesn't look bad, but I want an ACK from the
> > cgroup people -- specifically if they're OK with the filedesc juggling
> > thing, because I know the sysfs people objected to such tricks.
> >
>
> Long long ago, a feature that used this trick was accepted, and that's
> cgroup taskstat.
>
> You get an fd of a cgroup directory and send it to the kernel via netlink,
> and then you'll receive some statistics, such as how many tasks are
> running/interrupted in that cgroup.
>
That is right, since cgroups don't have id's there is no easy way to
identify them, looking them up by name and passing strings seemed an
overkill.
--
Three Cheers,
Balbir
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