Re: madvise(2) MADV_SEQUENTIAL behavior

From: Rik van Riel
Date: Thu Jul 17 2008 - 10:20:46 EST

On Wed, 16 Jul 2008 17:05:14 -0400
Chris Snook <csnook@xxxxxxxxxx> wrote:

> > I believe that for mmap MADV_SEQUENTIAL, we will have to do
> > an unmap-behind from the fault path. Not every time, but
> > maybe once per megabyte, unmapping the megabyte behind us.
> >
> > That way the normal page cache policies (use once, etc) can
> > take care of page eviction, which should help if the file
> > is also in use by another process.
> Wouldn't it just be easier to not move pages to the active list when
> they're referenced via an MADV_SEQUENTIAL mapping?

You want to check the MADV_SEQUENTIAL hint at pageout time and
discard the referenced bit from the pte?

> If we keep them on the inactive list, they'll be candidates for
> reclaiming

Only if we ignore the referenced bit. Which I guess we can do.

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