linux-kernel - Re: endless sync on bdi_sched

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Message-ID: <20100401111357.GA6601@dastard>
Date:	Thu, 1 Apr 2010 22:13:57 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Denys Fedorysychenko <nuclearcat@...learcat.com>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: endless sync on bdi_sched_wait()? 2.6.33.1

On Thu, Apr 01, 2010 at 01:42:42PM +0300, Denys Fedorysychenko wrote:
> Thats correct, it is quite busy cache server.
> 
> Well, if i stop squid(cache) sync will finish enough fast.
> If i don't - it took more than hour. Actually i left that PC after 1 hour, and 
> it didn't finish yet. I don't think it is normal.
> Probably sync taking new data and trying to flush it too, and till he finish 
> that, more data comes. 
> Actually all what i need - to sync config directory. I cannot use fsync, 
> because it is multiple files opened before by other processes, and sync is 
> doing trick like this. I got dead process, and only fast way to recover system 
> - kill the cache process, so I/O pumping will stop for a while, and sync() 
> will have chance to finish.
> Sure there is way just to "remount" config partition to ro, but i guess just 
> sync must flush only current buffer cache pages.
> 
> I will do more tests now and will give exact numbers, how much time it needs 
> with running squid and if i kill it shortly after running sync.

Ok. What would be interesting is regular output from /proc/meminfo
to see how the dirty memory is changing over the time the sync is
running....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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