Re: [PATCH 3/3] Provide control over unmapped pages

Balbir Singh
2010-12-05T05:14:19Z

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-12-02 11:50:36]:

> On Thu, 2 Dec 2010 10:22:16 +0900 (JST)
> KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
>
> > > On Tue, 30 Nov 2010, Andrew Morton wrote:
> > >
> > > > > +#define UNMAPPED_PAGE_RATIO 16
> > > >
> > > > Well. Giving 16 a name didn't really clarify anything. Attentive
> > > > readers will want to know what this does, why 16 was chosen and what
> > > > the effects of changing it will be.
> > >
> > > The meaning is analoguous to the other zone reclaim ratio. But yes it
> > > should be justified and defined.
> > >
> > > > > Reviewed-by: Christoph Lameter <cl@linux.com>
> > > >
> > > > So you're OK with shoving all this flotsam into 100,000,000 cellphones?
> > > > This was a pretty outrageous patchset!
> > >
> > > This is a feature that has been requested over and over for years. Using
> > > /proc/vm/drop_caches for fixing situations where one simply has too many
> > > page cache pages is not so much fun in the long run.
> >
> > I'm not against page cache limitation feature at all. But, this is
> > too ugly and too destructive fast path. I hope this patch reduce negative
> > impact more.
> >
>
> And I think min_mapped_unmapped_pages is ugly. It should be
> "unmapped_pagecache_limit" or some because it's for limitation feature.
>

The feature will now be enabled with a CONFIG and boot parameter, I
find changing the naming convention now - it is already in use and
well known is not a good idea. THe name of the boot parameter can be
changed of-course.

--
Three Cheers,
Balbir