Re: [RFC/T/D][PATCH 2/2] Linux/Guest cooperative unmapped pagecache control

From: KAMEZAWA Hiroyuki
Date: Thu Jun 10 2010 - 21:59:17 EST

On Thu, 10 Jun 2010 17:07:32 -0700
Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote:

> On Thu, 2010-06-10 at 19:55 +0530, Balbir Singh wrote:
> > > I'm not sure victimizing unmapped cache pages is a good idea.
> > > Shouldn't page selection use the LRU for recency information instead
> > > of the cost of guest reclaim? Dropping a frequently used unmapped
> > > cache page can be more expensive than dropping an unused text page
> > > that was loaded as part of some executable's initialization and
> > > forgotten.
> >
> > We victimize the unmapped cache only if it is unused (in LRU order).
> > We don't force the issue too much. We also have free slab cache to go
> > after.
> Just to be clear, let's say we have a mapped page (say of /sbin/init)
> that's been unreferenced since _just_ after the system booted. We also
> have an unmapped page cache page of a file often used at runtime, say
> one from /etc/resolv.conf or /etc/passwd.

Hmm. I'm not fan of estimating working set size by calculation
based on some numbers without considering history or feedback.

Can't we use some kind of feedback algorithm as hi-low-watermark, random walk
or GA (or somehing more smart) to detect the size ?


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