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Re: xfssyncd syncing every five seconds?

To: Jeremy Field <jezza@xxxxxxxxx>
Subject: Re: xfssyncd syncing every five seconds?
From: Nathan Scott <nathans@xxxxxxx>
Date: Thu, 18 Sep 2003 13:43:29 +1000
Cc: linux-xfs@xxxxxxxxxxx
In-reply-to: <20030918025301.GA18791@wylde.fl.net.au>; from jezza@fl.net.au on Thu, Sep 18, 2003 at 12:53:01PM +1000
References: <20030918020632.GA18362@wylde.fl.net.au> <20030918122113.A6939@wobbly.melbourne.sgi.com> <20030918025301.GA18791@wylde.fl.net.au>
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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.

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     0       0       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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