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    SubjectRe: [RFC][PATCH] oom_kill: avoid depends on total_vm and use real RSS/swap value for oom_score (Re: Memory overcommit
    On Tue, 27 Oct 2009, KAMEZAWA Hiroyuki wrote:
    > Now, oom-killer's score uses mm->total_vm as its base value.
    > But, in these days, applications like GUI program tend to use
    > much shared libraries and total_vm grows too high even when
    > pages are not fully mapped.
    >
    > For example, running a program "mmap" which allocates 1 GBbytes of
    > anonymous memory, oom_score top 10 on system will be..
    >
    > score PID name
    > 89924 3938 mixer_applet2
    > 90210 3942 tomboy
    > 94753 3936 clock-applet
    > 101994 3919 pulseaudio
    > 113525 4028 gnome-terminal
    > 127340 1 init
    > 128177 3871 nautilus
    > 151003 11515 bash
    > 256944 11653 mmap <-----------------use 1G of anon
    > 425561 3829 gnome-session
    >
    > No one believes gnome-session is more guilty than "mmap".
    >
    > Instead of total_vm, we should use anon/file/swap usage of a process, I think.
    > This patch adds mm->swap_usage and calculate oom_score based on
    > anon_rss + file_rss + swap_usage.
    > Considering usual applications, this will be much better information than
    > total_vm. After this patch, the score on my desktop is
    >
    > score PID name
    > 4033 3176 gnome-panel
    > 4077 3113 xinit
    > 4526 3190 python
    > 4820 3161 gnome-settings-
    > 4989 3289 gnome-terminal
    > 7105 3271 tomboy
    > 8427 3177 nautilus
    > 17549 3140 gnome-session
    > 128501 3299 bash
    > 256106 3383 mmap
    >
    > This order is not bad, I think.
    >
    > Note: This adss new counter...then new cost is added.

    I've often thought we ought to supply such a swap_usage statistic;
    and show it in /proc/pid/statsomething, presumably VmSwap in
    /proc/pid/status, even an additional field on the end of statm.

    A slight new cost, yes: doesn't matter at the swapping end, but
    would slightly impact fork and exit - I do hope we can afford it,
    because I think it should have been available all along.

    I've not checked your patch in detail; but I do agree that basing
    OOM (physical memory) decisions on total_vm (virtual memory) has
    seemed weird, so it's well worth trying this approach. Whether swap
    should be included along with rss isn't quite clear to me: I'm not
    saying you're wrong, not at all, just that it's not quite obvious.

    I've several observations to make about bad OOM kill decisions,
    but it's probably better that I make them in the original
    "Memory overcommit" thread, rather than divert this thread.

    Hugh


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