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    SubjectRe: [RFC mm][PATCH 5/5] counting lowmem rss per mm
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    On Thu, Dec 10, 2009 at 5:01 PM, KAMEZAWA Hiroyuki
    <kamezawa.hiroyu@jp.fujitsu.com> wrote:
    > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    >
    > Some case of OOM-Kill is caused by memory shortage in lowmem area. For example,
    > NORMAL_ZONE is exhausted on x86-32/HIGHMEM kernel.
    >
    > Now, oom-killer doesn't have no lowmem usage information of processes and
    > selects victim processes based on global memory usage information.
    > In bad case, this can cause chains of kills of innocent processes without
    > progress, oom-serial-killer.
    >
    > For making oom-killer lowmem aware, this patch adds counters for accounting
    > lowmem usage per process. (patches for oom-killer is not included in this.)
    >
    > Adding counter is easy but one of concern is the cost for new counter.
    >
    > Following is the test result of micro-benchmark of parallel page faults.
    > Bigger page fault number indicates better scalability.
    > (measured under USE_SPLIT_PTLOCKS environemt)
    > [Before lowmem counter]
    >  Performance counter stats for './multi-fault 2' (5 runs):
    >
    >       46997471  page-faults                ( +-   0.720% )
    >     1004100076  cache-references           ( +-   0.734% )
    >      180959964  cache-misses               ( +-   0.374% )
    >  29263437363580464  bus-cycles                 ( +-   0.002% )
    >
    >   60.003315683  seconds time elapsed   ( +-   0.004% )
    >
    > 3.85 miss/faults
    > [After lowmem counter]
    >  Performance counter stats for './multi-fault 2' (5 runs):
    >
    >       45976947  page-faults                ( +-   0.405% )
    >      992296954  cache-references           ( +-   0.860% )
    >      183961537  cache-misses               ( +-   0.473% )
    >  29261902069414016  bus-cycles                 ( +-   0.002% )
    >
    >   60.001403261  seconds time elapsed   ( +-   0.000% )
    >
    > 4.0 miss/faults.
    >
    > Then, small cost is added. But I think this is within reasonable
    > range.
    >
    > If you have good idea for improve this number, it's welcome.
    >
    > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Reviewed-by: Minchan Kim <minchan.kim@gmail.com>

    --
    Kind regards,
    Minchan Kim
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