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Re: xfssyncd syncing every five seconds?

To: "Nathan Scott" <nathans@xxxxxxx>
Subject: Re: xfssyncd syncing every five seconds?
From: "Simon Matter" <simon.matter@xxxxxxxxxxxxxxxx>
Date: Fri, 19 Sep 2003 01:13:28 +0200 (CEST)
Cc: "Jeremy Field" <jezza@xxxxxxxxx>, linux-xfs@xxxxxxxxxxx
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> On Thu, Sep 18, 2003 at 12:53:01PM +1000, Jeremy Field wrote:
>> Thanks for your exceedingly rapid reply...
>>
>> >> I am using linux 2.4.21 with xfs 1.3 on debian-unstable. Since I
>> >> upgraded from 2.4.18-xfs-1.1, my xfs partitions have been showing
>> >> pulses of activity every five seconds, I think because of xfssyncd.
>> >> The hard drive physically seeks every five seconds too.
>> >>
>> >> I have reviewed this mailing list and elsewhere for clues, but can't
>> >> work out either:
>> >>   a) whether this behaviour is normal, or
>> >>   b) how to change the interval.
>> >
>> > A sysctl variable controls this: /proc/sys/fs/xfs/sync_interval
>>
>> Ok I hadn't realised that's where it lived. Mine's set to "3000". Does
>> this value rule out the diagnosis I've made?
>
> thats every 30 seconds, so its unlikely to be xfssyncd.
>
>> > >>From Documentation/filesystems/xfs.txt...
>> >
>> >   fs.xfs.sync_interval          (Min: HZ  Default: 30*HZ  Max: 60*HZ)
>> >         The interval at which the xfssyncd thread for xfs filesystems
>> >         flushes metadata out to disk. This thread will flush log
>> >         activity out, and do some processing on unlinked inodes
>> >
>> > What makes you suspect xfssyncd?  It could also be some arbitrary
>> > process deciding to write something out every few seconds of course.
>>
>> The reason I suspect xfssyncd is because it happens simultaneously on
>> all of one drive's xfs partitions together (ie /{,usr,var,home}), and
>> not on its non-xfs partitions. Additionally, this behaviour is new since
>> I upgraded to xfs 1.3.

I just wanted to say 'me too'. And I can confirm that it's new with 1.3, I
have never seen this with any XFS version before. I have exactly the same
kernels with XFS 1.2 and 1.3 and it only happens with 1.3.
If you have a filesystem spread over lots of spindles, it sound a bit
scary, every 5 seconds.

Simon

>
> hmmm.
>
>> It doesn't actually seem to be happening on another drive which has a
>> mounted xfs partition. Some other possibly relevant settings:
>>
>>     $ cat /proc/sys/vm/bdflush
>>     30      500                   500     3000    60      20      0
>>                                  ^ interval in 1/100s between kupdate
>>                                  flushes -- could this be my problem?
>
> possibly.  worth fiddling with that knob and seeing what happens,
> anyway.
>
> cheers.
>
> --
> Nathan
>
>
>



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