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Re: XFS performance oddity

To: Nick Piggin <npiggin@xxxxxxxxx>
Subject: Re: XFS performance oddity
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 24 Nov 2010 07:58:04 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20101123122449.GA4812@amd>
References: <20101123122449.GA4812@amd>
User-agent: Mutt/1.5.20 (2009-06-14)
On Tue, Nov 23, 2010 at 11:24:49PM +1100, Nick Piggin wrote:
> Hi,
> 
> Running parallel fs_mark (0 size inodes, fsync on close) on a ramdisk
> ends up with XFS in funny patterns.
> 
> procs -----------memory---------- ---swap-- -----io---- -system--
> ----cpu----
>  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy
> id wa
> 24  1   6576 166396    252 393676  132  140 16900 80666 21308 104333  1 84 14 
>  1
> 21  0   6712 433856    256 387080  100  224  9152 53487 13677 53732  0 55 45  > 0
>  2  0   7068 463496    248 389100    0  364  2940 17896 4485 26122  0 33 65  2
>  1  0   7068 464340    248 388928    0    0     0     0   66  207  0  0 100  0
>  0  0   7068 464340    248 388928    0    0     0     0   79  200  0  0 100  0
>  0  0   7068 464544    248 388928    0    0     0     0   65  199  0  0 100  0
>  1  0   7068 464748    248 388928    0    0     0     0   79  201  0  0 100  0
>  0  0   7068 465064    248 388928    0    0     0     0   66  202  0  0 100  0
>  0  0   7068 465312    248 388928    0    0     0     0   80  200  0  0 100  0
>  0  0   7068 465500    248 388928    0    0     0     0   65  199  0  0 100  0
>  0  0   7068 465500    248 388928    0    0     0     0   80  202  0  0 100  0
>  1  0   7068 465500    248 388928    0    0     0     0   66  203  0  0 100  0
>  0  0   7068 465500    248 388928    0    0     0     0   79  200  0  0 100  0
> 23  0   7068 460332    248 388800    0    0  1416  8896 1981 7142  0  1 99  0
>  6  0   6968 360248    248 403736   56    0 15568 95171 19438 110825  1 79 21 
>  0
> 23  0   6904 248736    248 419704  392    0 17412 118270 20208 111396  1 82 
> 17  0
>  9  0   6884 266116    248 435904  128    0 14956 79756 18554 118020  1 76 23 
>  0
>  0  0   6848 219640    248 445760  212    0  9932 51572 12622 76491  0 60 40  > 0
> 
> Got a dump of sleeping tasks. Any ideas?

It is stuck waiting for log space to be freed up. Generally this is
caused by log IO completion not occurring or an unflushable object
preventing the tail from being moved forward.  What:

        - kernel are you running?
        - is the time resolution of the above output?
        - is the output of mkfs.xfs?
        - are your mount options?
        - is the fs_mark command line?

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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