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

Bharata B Rao
2005-09-12T12:53:48Z

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.