Messages in this thread | | | Date | Fri, 26 Nov 2010 08:26:05 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH 1/2] perf_events: add support for per-cpu per-cgroup monitoring (v5) |
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* lizf@cn.fujitsu.com <lizf@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 <eranian@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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