Re: [PATCH 20/20] Get rid of the concept of hot/cold page freeing

Andrew Morton
2009-02-25T00:02:26Z

On Tue, 24 Feb 2009 11:51:26 +0000
Mel Gorman <mel@csn.ul.ie> wrote:

> > > Almost the opposite with steady improvements almost all the way through.
> > >
> > > With the patch applied, we are still using hot/cold information on the
> > > allocation side so I'm somewhat surprised the patch even makes much of a
> > > difference. I'd have expected the pages being freed to be mostly hot.
> >
> > Oh yeah. Back in the ancient days, hot-cold-pages was using separate
> > magazines for hot and cold pages. Then Christoph went and mucked with
> > it, using a single queue. That might have affected things.
> >
>
> It might have. The impact is that requests for cold pages can get hot pages
> if there are not enough cold pages in the queue so readahead could prevent
> an active process getting cache hot pages. I don't think that would have
> showed up in the microbenchmark though.

We switched to doing non-temporal stores in copy_from_user(), didn't
we? That would rub out the benefit which that microbenchmark
demonstrated?