quotacheck speed

[Christoph Hellwig]

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.  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?