Re: [dm-devel] New dm-bufio with shrinker API

[Joe Thornber <thornber redhat com>]

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