Re: xfs_repair segfaults with ag_stride option

Eric Sandeen
2012-02-06T13:21:34Z

On 2/6/12 5:19 AM, Tom Crane wrote:
> Eric Sandeen wrote:

...

>> Newer tools are fine to use on older filesystems, there should be no
>>
>
> Good!
>
>> issue there.
>>
>> running fsr can cause an awful lot of IO, and a lot of file reorganization.
>> (meaning, they will get moved to new locations on disk, etc).
>>
>> How bad is it, really? How did you arrive at the 40% number? Unless
>>
>
> xfs_db -c frag -r <block device>

which does:

answer = (double)(extcount_actual - extcount_ideal) * 100.0 /
(double)extcount_actual;

If you work it out, if every file was split into only 2 extents, you'd have
"50%" - and really, that's not bad. 40% is even less bad.

> Some users on our compute farm with large jobs (lots of I/O) find they take longer than with some of our other scratch arrays hosted on other machines. We also typically find many nfsd tasks in an uninterruptible wait state (sync_page), waiting for data to be copied in from the FS.

So fragmentation may not be the problem...

-Eric

>> you see perf problems which you know you can attribute to fragmentation,
>> I might not worry about it.
>>
>> You can also check the fragmentation of individual files with the
>> xfs_bmap tool.
>>
>> -Eric
>>
>
> Thanks for your advice.
> Cheers
> Tom.
>
>>
>>> Tom.
>>>
>>> Christoph Hellwig wrote:
>>>
>>>> Hi Tom,
>>>>
>>>> On Wed, Feb 01, 2012 at 01:36:12PM +0000, Tom Crane wrote:
>>>>
>>>>
>>>>> Dear XFS Support,
>>>>> I am attempting to use xfs_repair to fix a damaged FS but always
>>>>> get a segfault if and only if -o ag_stride is specified. I have
>>>>> tried ag_stride=2,8,16 & 32. The FS is approx 60T. I can't find
>>>>> reports of this particular problem on the mailing list archive.
>>>>> Further details are;
>>>>>
>>>>> xfs_repair version 3.1.7, recently downloaded via git repository.
>>>>> uname -a
>>>>> Linux store3 2.6.18-274.17.1.el5 #1 SMP Wed Jan 11 11:10:32 CET 2012
>>>>> x86_64 x86_64 x86_64 GNU/Linux
>>>>>
>>>> Thanks for the detailed bug report.
>>>>
>>>> Can you please try the attached patch?
>>>>
>>>>
>>> _______________________________________________
>>> xfs mailing list
>>> xfs@oss.sgi.com
>>> http://oss.sgi.com/mailman/listinfo/xfs