Date: Mon, 12 Sep 2005 18:23:28 +0530
From: Bharata B Rao <bharata@in.ibm.com>
To: "Martin J. Bligh" <mbligh@mbligh.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>, Dipankar Sarma <dipankar@in.ibm.com>,
       linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: VM balancing issues on 2.6.13: dentry cache not getting shrunk enough
Message-ID: <20050912125327.GB3804@in.ibm.com>
Reply-To: bharata@in.ibm.com
References: <20050911105709.GA16369@thunk.org> <20050911120045.GA4477@in.ibm.com> <20050912031636.GB16758@thunk.org> <210180000.1126505790@[10.10.2.4]>
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On Sun, Sep 11, 2005 at 11:16:30PM -0700, Martin J. Bligh wrote:
> 
> 
> --Theodore Ts'o <tytso@mit.edu> wrote (on Sunday, September 11, 2005 23:16:36 -0400):
> 
> > On Sun, Sep 11, 2005 at 05:30:46PM +0530, Dipankar Sarma wrote:
> >> Do you have the /proc/sys/fs/dentry-state output when such lowmem
> >> shortage happens ?
> > 
> > Not yet, but the situation occurs on my laptop about 2 or 3 times
> > (when I'm not travelling and so it doesn't get rebooted).  So
> > reproducing it isn't utterly trivial, but it's does happen often
> > enough that it should be possible to get the necessary data.
> >
> >> This is a problem that Bharata has been investigating at the moment.
> >> But he hasn't seen anything that can't be cured by a small memory
> >> pressure - IOW, dentries do get freed under memory pressure. So
> >> your case might be very useful. Bharata is maintaing an instrumentation
> >> patch to collect more information and an alternative dentry aging patch 
> >> (using rbtree). Perhaps you could try with those.
> > 
> > Send it to me, and I'd be happy to try either the instrumentation
> > patch or the dentry aging patch.
> 
> Other thing that might be helpful is to shove a printk in prune_dcache
> so we can see when it's getting called, and how successful it is, if the
> more sophisticated stuff doesn't help ;-)
> 

I have incorporated this in the dcache stats patch I have. I will 
post it tommorrow after adding some more instrumentation data
(number of inuse and free dentries in lru list) and after a bit of
cleanup and testing.

Regards,
Bharata.
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