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

Andrew Morton
2009-05-01T01:18:25Z

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

> On Thu, 30 Apr 2009 17:45:36 -0700
> Andrew Morton <akpm@linux-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?