Re: [RFC] Arch option to touch newly allocated pages

Andrew Morton
2002-03-07T20:59:02Z

Rik van Riel wrote:
>
> On Thu, 7 Mar 2002, Andrew Morton wrote:
> > Daniel Phillips wrote:
> > >
> > > a GFP flag that says 'fail if this looks hard to get'.
> >
> > Something like that would provide a solution to the
> > readahead thrashing problem.
>
> Nope. Readahead pages are clean and very easy to evict, so
> it's still trivial to evict all the pages from another readahead
> window because everybody's readahead window is too large.
>

I was thinking an explicit GFP_READAHEAD and PG_readahead.
Where a GFP_READAHEAD allocation would fail if it can't
find any non-readahead pages. And it would fail if it
had to perform I/O.

That's not nice - it'd result in large LRU walks. But it'd
be better than the 10x slowdown which readahead thrashing
causes.

Any clever ideas?

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