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Subject: Re: [PATCH 1/2] perf_events: add support for per-cpu per-cgroup
 monitoring (v5)
From: Peter Zijlstra <peterz@infradead.org>
To: eranian@google.com
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, paulus@samba.org,
        davem@davemloft.net, fweisbec@gmail.com, perfmon2-devel@lists.sf.net,
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        lizf@cn.fujitsu.com, Paul Menage <menage@google.com>,
        Balbir Singh <balbir@in.ibm.com>, Greg Kroah-Hartman <gregkh@suse.de>
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Date: Thu, 25 Nov 2010 12:28:43 +0100
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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.

Also, it might make sense to add a CONFIG_PERF_CGROUP, even if you want
it automagically set if CONFIG_PERF && CONFIG_CGROUP, its easier to find
all related code if its under a single CONFIG_var.