Re: xfs corrupted

[Stefanita Rares Dumitrescu <katmai@keptprivate.com>]

Quick update:

The xfsprogs from the centos6 yum are newer and they don't use that much 
memory, however i got 2 segfaults and the process stopped.

I cloned the xfsprogs git and i am running it now with the new 15 gb 
swap that i created, and this is a monster in memory usage.

Pretty bit of discrepancy.

On 15/10/2013 22:26, Dave Chinner wrote:
> On Tue, Oct 15, 2013 at 09:57:47PM +0200, Stefanita Rares Dumitrescu wrote:
>> Since i am using centos 5.9, the version of the xfsprogs seems to be
>> old, so i cloned the new one from sgi.
>>
>> I have a machine with 4 gb ram, and 4 gb swap, and it's all been
>> eaten up by xfs_repair, and slowed down to a crawl.
>>
>> the sdc partition is the one being checked. i am all out of memory
>> now. 4 gb phys and 4 gb swap all gone.
>>
>> http://pastebin.ca/2467064
>>
>> posted to pastebin for better formatting.
>>
>> i was using:
>>
>> [root@kp4 ~]# xfs_repair -o bhash=16384 -o ihash=16384 -o ag_stride=16 \
>>> /dev/sdc >& /tmp/repair.log
>
> You don't have enough RAM to run threaded prefetching and parallel
> AG processing. You'd do better to turn prefetching off entirely with
> "-P" if you are having OOM problems.
>
>> but now i am trying the -m option to see if the memory can be
>> limited, so the server doesn't freeze.
>>
>> [root@kp4 ~]# xfs_repair -m 3072 -o ag_stride=16 /dev/sdc >& /tmp/repair.log
>>
>> nothing in dmesg either.
>
> Give it another 10-20GB of swap, and it should be fine. xfs_repair
> usually only thrashes swap when you don't have enough of it and it
> keeps trying to free memory, paging in pages that are in swap to
> free cached objects from them. Most of the memory references that
> repair makes are quite local, so when pages are swapped out they
> generally aren't needed again for a while except when cache reclaim
> kicks in. Hence if you give it enough swap that it can grow without
> bounds, then it should still be quite efficient.
>
> Keep in mind that badly corrupted filesystems require lots more
> memory than clean filesystems to check and repair as there is lots
> more intermediate state that repair needs to hold in memory about
> partially or incompletely referenced objects. Don't be surprised if
> the amount of memory needed to repair a badly broken filesystem is
> 10-100x the amount of RAM needed to run xfs_repair on the same clean
> filesystem....
>
> Cheers,
>
> Dave.
>

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