[dm-devel] New dm-bufio with shrinker API
Joe Thornber
thornber at redhat.com
Tue Sep 6 09:53:48 UTC 2011
On Mon, Sep 05, 2011 at 11:07:15AM -0400, Christoph Hellwig wrote:
> On Mon, Sep 05, 2011 at 03:49:14PM +0100, Joe Thornber wrote:
> > I changed the test suite to reset the peak_allocated parameter before
> > each test and record it at the end of each test. It's very hard to
> > say what is right and wrong when talking about cache sizes, since you
> > always have to qualify anything by saying 'for this particular load'.
> > However, I think bufio could be more aggressive about recycling cache
> > entries. With the old block manager the test suite ran nicely with
> > less than 256k, from memory I think I started seeing slow down around
> > 128k. With bufio I'm seeing consistently larger cache sizes for the
> > same performance.
>
> IS there any reason you'll need a fixed size? This is fairly similar in
> concept to the XFS buffercache, which does perfectly well by allocation
> memory as needed, and letting the shrinker reclaim buffers when under
> memory pressure.
Well if the shrinker does such a good job, do we really need to set a
maximum value for the cache size at all? (perhaps this was your
question and I'm being slow).
- Joe
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