Messages in this thread | | | Date | Tue, 27 Oct 2009 18:39:07 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: [RFC][PATCH] oom_kill: avoid depends on total_vm and use real RSS/swap value for oom_score (Re: Memory overcommit |
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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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