linux-kernel - Re: [PATCH] vmscan: evict use-once pages first (v2)

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Message-Id: <20090430181340.6f07421d.akpm@linux-foundation.org>
Date:	Thu, 30 Apr 2009 18:13:40 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	elladan@...imo.com, peterz@...radead.org,
	linux-kernel@...r.kernel.org, tytso@....edu,
	kosaki.motohiro@...fujitsu.com, linux-mm@...ck.org
Subject: Re: [PATCH] vmscan: evict use-once pages first (v2)

On Thu, 30 Apr 2009 20:59:36 -0400
Rik van Riel <riel@...hat.com> wrote:

> On Thu, 30 Apr 2009 17:45:36 -0700
> Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> > Were you able to tell whether altering /proc/sys/vm/swappiness
> > appropriately regulated the rate at which the mapped page count
> > decreased?
> 
> That should not make a difference at all for mapped file
> pages, after the change was merged that makes the VM ignores
> the referenced bit of mapped active file pages.
> 
> Ever since the split LRU code was merged, all that the
> swappiness controls is the aggressiveness of file vs
> anonymous LRU scanning.

Which would cause exactly the problem Elladan saw?

> Currently the kernel has no effective code to protect the 
> page cache working set from streaming IO.  Elladan's bug
> report shows that we do need some kind of protection...

Seems to me that reclaim should treat swapcache-backed mapped mages in
a similar fashion to file-backed mapped pages?

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