Setting oom_adj on linux?
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From: Magnus Hagander on 4 Jan 2010 11:59 On Mon, Jan 4, 2010 at 17:55, Alvaro Herrera <alvherre(a)commandprompt.com> wrote: > Magnus Hagander wrote: > >> Right. Which is why I like the idea of disabling the OOM killer for >> the *postmaster*, but not the regular backends. Gives it a chance to >> recover. It's not nice, but it's better than nothing. > > It doesn't sound like the init script can reenable the killer for the > child processes though. So, if there's anything that the core code > ought to do, is re-enable OOM-killer for postmaster children, after > being disabled by the initscript. Yeah, that's why the backend code would need to be involved. > BTW, is it possible for pg_ctl to disable OOM-killer? I guess not, > since it's not run by root ... No, it has to run as root. > Is there a way to disable memory overcommit for particular processes? > That would be very useful -- just disable overcommit for all Postgres > processes, and there shouldn't be much need to enable the killer for > backends. Not that I've been able to find. -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/ -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Tom Lane on 4 Jan 2010 11:59 Alvaro Herrera <alvherre(a)commandprompt.com> writes: > Is there a way to disable memory overcommit for particular processes? I would think not --- the very essence of overcommit is that you're promising more total memory than the system has got, and that's inherently a global proposition. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Alvaro Herrera on 4 Jan 2010 12:00 Magnus Hagander wrote: > On Mon, Jan 4, 2010 at 17:55, Alvaro Herrera <alvherre(a)commandprompt.com> wrote: > > BTW, is it possible for pg_ctl to disable OOM-killer? �I guess not, > > since it's not run by root ... > > No, it has to run as root. We could at least make it work on Windows, since it is often run as Administrator and drops privileges afterwards ... .... oh, wait ... -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc. -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: Tom Lane on 4 Jan 2010 13:09 Magnus Hagander <magnus(a)hagander.net> writes: > I realize this is a very platform-specific thing, but should we > consider setting the value of /proc/<pid>/oom_adj when running on > linux? See: > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/filesystems/proc.txt;h=220cc6376ef80e0c9bcfec162d45552e729cdf5a;hb=45d28b097280a78893ce25a5d0db41e6a2717853 One interesting thing I read there is: Swapped out tasks are killed first. Half of each child's memory size is added to the parent's score if they do not share the same memory. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This suggests that PG's shared memory ought not be counted in the postmaster's OOM score, which would mean that the problem shouldn't be quite as bad as we've believed. I wonder if that is a recent change? Or maybe it's supposed to be that way and is not implemented correctly? BTW, the given link shows only chapter 1, see http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob_plain;f=Documentation/filesystems/proc.txt;hb=45d28b097280a78893ce25a5d0db41e6a2717853 for the whole file. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
From: "Kevin Grittner" on 4 Jan 2010 13:32
Tom Lane <tgl(a)sss.pgh.pa.us> wrote: > This suggests that PG's shared memory ought not be counted in the > postmaster's OOM score, which would mean that the problem > shouldn't be quite as bad as we've believed. I wonder if that is > a recent change? Or maybe it's supposed to be that way and is not > implemented correctly? I've wondered about that based on my experience. When I found that memory leak back in 8.2devel, running on a SLES 9 SP 3 system, the OOM killer killed the offending backend rather than the postmaster, although it took out a couple Java middle tier processes before starting in on PostgreSQL. -Kevin -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers |