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

KAMEZAWA Hiroyuki
2010-12-02T02:56:26Z

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.

Thanks,
-Kame