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Re: quotacheck speed

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: quotacheck speed
From: Arkadiusz Miśkiewicz <arekm@xxxxxxxx>
Date: Wed, 15 Feb 2012 11:39:10 +0100
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
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On Tuesday 14 of February 2012, Arkadiusz Miśkiewicz wrote:
> On Tuesday 14 of February 2012, Dave Chinner wrote:
> > On Mon, Feb 13, 2012 at 07:09:50PM +0100, Arkadiusz Miśkiewicz wrote:
> > > On Monday 13 of February 2012, Christoph Hellwig wrote:
> > > > On Sun, Feb 12, 2012 at 10:01:07PM +0100, Arkadiusz Mi??kiewicz wrote:
> > > > > Hi,
> > > > > 
> > > > > When mounting 800GB filesystem (after repair for example) here
> > > > > quotacheck takes 10 minutes. Quite long time that adds to whole
> > > > > time of filesystem downtime (repair + quotacheck).
> > > > > 
> > > > > I wonder if quotacheck can be somehow improved or done differently
> > > > > like doing it in parallel with normal fs usage (so there will be no
> > > > > downtime) ?
> > > > 
> > > > I think the best idea to improve the performance in case you did a
> > > > repair is to integrate the quotacheck code into repair.  It's fairly
> > > > simple given that quotacheck simply walks all inodes and adds their
> > > > space usage to the correct user/group/project, and given that repair
> > > > already walks all inodes, and checks their block maps it does most of
> > > > that work already.
> > > 
> > > That would be interesting and probably make
> > > 
> > > > The only downside would be that the memory usage
> > > > of repair increases a bit by keeping the dquots in memoryb, but even
> > > > for your 130000 dquot setup that would add about 100 bytes * 130000
> > > > please a bit of in-memory metadata (less than 20MB total) of memory
> > > > usage, so it probably is a good tradeoff.
> > > > 
> > > > 
> > > > In what cases do you regularly run quotacheck when you did not do
> > > > a repair first?
> > > 
> > > I don't initiate quotacheck manually. AFAIK internal xfs quotacheck
> > > happens in two cases here:
> > > 1) repair->mount
> > > 2) filesystem has quotacheck done properly some time ago -> umount ->
> > > mount-
> > > 
> > > >oops/reset/something like that happens while mounting -> new mount
> > 
> > So you'd like both quotacheck to be sped up and repair
> > to do it as well? ;)
> 
> Well, 1) is happening much more often than 2) :-)

Oh, and one more scenario. Running system, sysrq u, s, b -> new boot, mount -> 
quotacheck runs.

Does it need to run in such case?

-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/

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