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

Theodore Ts'o
2005-09-14T22:46:13Z

On Wed, Sep 14, 2005 at 02:43:13AM -0700, Andrew Morton wrote:
> Manfred Spraul <manfred@colorfullife.com> wrote:
> >
> > One tricky point are directory dentries: As far as I see, they are
> > pinned and unfreeable if a (freeable) directory entry is in the cache.
> >
>
> Well. That's the whole problem.
>
> I don't think it's been demonstrated that Ted's problem was caused by
> internal fragementation, btw. Ted, could you run slabtop, see what the
> dcache occupancy is? Monitor it as you start to manually apply pressure?
> If the occupancy falls to 10% and not many slab pages are freed up yet then
> yup, it's internal fragmentation.

The next time I can get my machine into that state, sure, I'll try it.
I used to be able to reproduce it using normal laptop usage patterns
(Lotus notes running under wine, kernel builds, apt-get upgrade's,
openoffice, firefox, etc.) about twice a week with 2.6.13-rc5, but
with 2.6.13, it happened once or twice, but since then I haven't been
able to trigger it. (Predictably, not after I posted about it on
LKML. :-/)

I've been trying a few things in the hopes of deliberately triggering
it, but so far, no luck. Maybe I should go back to 2.6.13-rc5 and see
if I have an easier time of reproducing the failure case.

- Ted