Re: [RFC] Limit the size of the pagecache

[Aubrey Li]

On 1/25/07, Vaidyanathan Srinivasan <svaidy@xxxxxxxxxxxxxxxxxx> wrote:
> Christoph Lameter wrote:
> > On Wed, 24 Jan 2007, Vaidyanathan Srinivasan wrote:
> >
> >> With your patch, MMAP of a file that will cross the pagecache limit hangs the
> >> system.  As I mentioned in my previous mail, without subtracting the
> >> NR_FILE_MAPPED, the reclaim will infinitely try and fail.
> >
> > Well mapped pages are still pagecache pages.
> >
>
> Yes, but they can be classified under a process RSS pages.  Whether it
> is an anon page or shared mem or mmap of pagecache, it would show up
> under RSS.  Those pages can be limited by RSS limiter similar to the
> one we are discussing in pagecache limiter.  In my opinion, once a
> file page is mapped by the process, then it should be treated at par
> with anon pages.  Application programs generally do not mmap a file
> page if the reuse for the content is very low.

I agree, we shouldn't take mmapped page into account.
But Vaidy - even with your patch, we are still using the existing
reclaimer, that means we dont ensure that only page cache is
reclaimed/limited. mapped pages will be hit also.
I think we still need to add a new scancontrol field to lock mmaped
pages and remove unmapped pagecache pages only.

-Aubrey
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