Re: PERF: performance tests with the split LRU VM in -mm

Rik van Riel
2008-07-28T23:57:13Z

On Mon, 28 Jul 2008 16:41:24 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> > Andrew, what is your preference between:
> > http://lkml.org/lkml/2008/7/15/465
> > and
> > http://marc.info/?l=linux-mm&m=121683855132630&w=2
> >
>
> Boy. They both seem rather hacky special-cases. But that doesn't mean
> that they're undesirable hacky special-cases. I guess the second one
> looks a bit more "algorithmic" and a bit less hacky-special-case. But
> it all depends on testing..

I prefer the second one, since it removes the + 1 magic (at least,
for the higher priorities), instead of adding new magic like the
other patch does.

> On a different topic, these:
>
> vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch
> vm-dont-run-touch_buffer-during-buffercache-lookups.patch
>
> have been floating about in -mm for ages, awaiting demonstration that
> they're a net benefit. But all of this new page-reclaim rework was
> built on top of those two patches and incorporates and retains them.
>
> I could toss them out, but that would require some rework and would
> partially invalidate previous testing and who knows, they _might_ be
> good patches. Or they might not be.
>
> What are your thoughts?

I believe you should definately keep those. Being able to better
preserve actively accessed file pages could be a good benefit and
we have yet to discover a downside to those patches.

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