Messages in this thread | | | Date | Fri, 3 Feb 2006 01:26:07 -0800 | From | Andrew Morton <> | Subject | Re: adding swap workarounds oom - was: Re: Out of Memory: Killed process 16498 (java). |
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Anton Altaparmakov <aia21@cam.ac.uk> wrote: > > Hi, > > On Fri, 2006-01-27 at 14:39 +0000, Anton Altaparmakov wrote: > > A colleague has a server (which does backups) that is incapable of doing > > a backup due to the backup process being killed due to OOM after > > anywhere between 30s and a few minutes of running... And the backup > > process is just a simple program that does the equivalent of "dd with > > one source but two destinations" where the source is an lvm/dm snapshot > > and the two destinations are two different tape drives attached via > > scsi. That is pretty critical, admittedly only to us and that system... > > We found a workaround for the OOM problems on above server yesterday. > > Add a 1MiB swap file: > > dd if=/dev/zero of=/var/swapfile bs=1024 count=1024 > mkswap /var/swapfile > swapon /var/swapfile > > Run backup script and no problems! > > Note: This is a suse SLES9 system and the problem is not present on > kernel kernel-smp-2.6.5-7.193.i586.rpm and all earlier kernels and it is > present on kernel-smp-2.6.5-7.201.i586.rpm and all later kernels > including the latest kernel (2.6.5-7.244). > > Seems like a definite VM bug... Interestingly on the .244 kernel the > OOM conditions print out a lot of debug information to dmesg about the > memory use in the system and AFAICS none of the memory is exhausted! So > it seems the system goes OOM without it actually being OOM because it > detects that "free swap == 0" or something along those lines...
It does sound like that. Does it still happen if there's 1MB of swap online and it's all full?
> Or do we nowadays require swap to be present?
Shouldn't be the case.
> The machine has 6GiB RAM so swap was turned off on it. (In our > experience if a machine with a lot of concurrent connections starts > swapping the system goes down the drain (it becomes too slow) so swap is > not something we want on servers with 40000+ users...)
1MB of swap isn't likely to cause a lot of swapping.
> If the above is not enough information to find/fix the problem please > let me know what more you would like to know...
It'd be nice to see the oom-killer output.
I don't recall a problem like this. I wonder if there are any suse changes which might have triggered it. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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