Re: VM balancing issues on 2.6.13: dentry cache not getting shrunk enough

Martin J. Bligh
2005-09-12T06:16:30Z

--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 ;-)

M.