Re: Kernel does strange things when compilations push memory usage above physical memory and the compilations are being done in a tmpfs, despite having ample swap

[Andrew Hendry]

Kame,

Could the tempfs revert be the same and fix the ramdisk issue I have seen?
http://marc.info/?l=linux-kernel&m=127569877714937&w=2
I can re-test this evening.

Andrew.

On Mon, Jun 21, 2010 at 1:02 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> On Sun, 20 Jun 2010 22:23:50 -0400
> Richard Yao <shiningarcanine@xxxxxxxxx> wrote:
>
>> My system is still responsive if it has not locked-up, even after the
>> oom-killer appears to have killed stuff.
>>
>> Does the kernel need to be compiled with any special options to have
>> it report to dmesg that the oom-killer activated? I cited the
>> oom-killer as being activated because several things would
>> inexplicit-ably crash when the system is under memory pressure, but
>> looking in my dmesg log at a crash that occurred earlier today when I
>> forgot to unmount my tmpfs, I do not see any references to the oom
>> killer, just the process that crashed:
>>
>
> Are your oom-killer happens  on workload on tmpfs ?
> (I thought /var/tmp isn' tmpfs..)
>
> plz check this.
> =
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d6da1a5abc2bf3a06a5bda08e0f6833409234666
> =
>
> Does oom-killer happens also on 2.6.33 ?
>
> Thanks,
> =Kame
>
>> [ 5873.816211] chrome[18404]: segfault at 8 ip 0000000001063b9b sp
>> 00007fffb0a7f540 error 4 in chrome[400000+28be000]
>>
>> Could it be that a bug is causing the kernel to map the same region of
>> physical memory to multiple programs?
>>
>> On Sun, Jun 20, 2010 at 10:03 PM, Andrew Hendry <andrew.hendry@xxxxxxxxx> wrote:
>> > After the oom killer has killed things, is your system still really
>> > sluggish if it doesn't lockup?
>> >
>> > I have what might be a similar issue, after a lot of compiling on a ramdisk.
>> > http://marc.info/?l=linux-kernel&m=127569877714937&w=2
>> >
>> > Oom killer keeps killing processes until almost nothing is left.
>> > Free memory is very high, and system is still very sluggish.
>> >
>> > On Mon, Jun 21, 2010 at 10:21 AM, Richard Yao <shiningarcanine@xxxxxxxxx> wrote:
>> >> Dear Everyone,
>> >>
>> >> My desktop has 4GB of RAM and it is running an unpatched Linux 2.6.34
>> >> kernel. I recently migrated it from Windows 7 to Gentoo Linux and I am
>> >> encountering a highly peculiar problem when I build/rebuild system
>> >> packages in a manner that stresses memory.
>> >>
>> >> When system memory usage exceeds 4GB because I have several
>> >> compilations running simultaneously, all of which have had -j5 passed
>> >> to make, with the build scripts sharing an 8GB tmpfs directory, the
>> >> system typically responds by activating the kernel oom-killer, which
>> >> will usually kill some of the processes involved in the compilations,
>> >> among other things. This is with an 8GB swap partition and barely any
>> >> of it is touched when this happens according to KDE's system monitor.
>> >> Rarer, but alternative responses that the system has made to such
>> >> circumstances involve the system package manager failing
>> >> mid-compilation with "Segmentation fault" printed to the console or
>> >> open office failing with an obscure error message. Usually just
>> >> compiling open office alone is enough to have things fail, although I
>> >> usually see it fail with an obscure 5 digit error message that has no
>> >> meaning which I can derive from doing searches with Google. Unmounting
>> >> my tmpfs directory and doing things as I normally would do them makes
>> >> these issues disappear.
>> >>
>> >> I have run memtest and it has not detected any hardware issues. I
>> >> tried asking for help on the Gentoo Linux forums, but I received no
>> >> responses and this looks like a kernel issue, so I thought it would be
>> >> a good idea to ask for assistance on the kernel mailing list. Here is
>> >> a link to a copy of my kernel's .config file:
>> >>
>> >> http://paste.pocoo.org/show/227799/
>> >>
>> >> As I was typing this, I had openoffice 3.2.1 and something else
>> >> compiling in the background and the system completely froze. This is
>> >> the first I have seen my system do this and it was about 10 minutes
>> >> after the oom-killer had already taken out kwin and several tabs in
>> >> chromium. I had SSH running in the background, but even that has been
>> >> rendered inaccessible by the freeze. I cannot get a response from the
>> >> system via arping and nmap is telling me that the system is down.
>> >>
>> >> Earlier today, I tried to reproduce this issue under simpler
>> >> cirumstances by doing dd bs=4096 count=2097152 if=/dev/zero
>> >> of=/var/tmp/portage/zero.bak. As a consequence of all of the swapping
>> >> that occurred, the system's X server become unresponsive, so I walked
>> >> away and came back a few minutes later to find that the KDE System
>> >> Monitor had crashed, but everything else seemed fine.
>> >>
>> >> Any help with this issue would be appreciated. I am willing to
>> >> recompile my system in whatever manner necessary to diagnose the cause
>> >> of this issue. Please CC me any responses made either directly or
>> >> indirectly in response to this message.
>> >>
>> >> Yours truly,
>> >> Richard Yao
>> >> --
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