Messages in this thread | | | Date | Fri, 26 Nov 2010 16:28:50 +0800 | From | Li Zefan <> | Subject | Re: [PATCH 1/2] perf_events: add support for per-cpu per-cgroup monitoring (v5) |
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Balbir Singh wrote: > * 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. >
More information:
Another feature recently added (eventfd-based notifications) also uses fd to identify a cgroup.
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