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    Subject[RFC PATCH 0/2] CPU controller statistics - v5

    Last year, Balaji posted a patch to collect CPU controller statistics. After
    a few initial versions, I couldn't see any activity. Here I am posting the
    next version of the patch for review.

    Changes for v5:

    - Updated to 2.6.29-rc6.
    - Separated cgroup modifications into a different patch.
    - Changed the prototype of the ->initialize() subsystem API from
    cgroup_subsys->initialize(int early) to cgroup_subsys->initialize(void)
    and calling it only from cgroup_init() and not from cgroup_init_early().
    - Updated documentation for new API.
    - Added guest time metric as another cpu controller statistic.
    - Free percpu statistics counters when the cgroup is brought down.
    - Account irq and softirq time also as system time for cgroup accounting.
    - Separate out stats collection code under CONFIG_CGROUP_SCHED to a helper
    funtion to reduce ifdefs.


    I have tried to address most of the comments given for the 4th version
    of the patch. A few questions still remain:

    - percpu counters are used for stats collection. Since percpu counters
    aren't usable during cgroup_init_early(), we have to allocate
    percpu stats counter for init_task_group separately later during
    cgroup_init(). Because of this, in the stats collection code, we
    end up having a 'is stats counter allocated?' check
    - This patch collects per cgroup cpu controller stats. Does it make
    sense to account stime and utime hierarchially ? If so, we would
    probably be duplicating what cpuacct controller already does.
    - Is steal time a useful per-cgroup metric ? Perhaps in container based
    virtualized environments ?


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