Re: [PATCH 1/5] page allocator: Always wake kswapd when restartingan allocation attempt after direct reclaim failed

[Mel Gorman]

On Thu, Oct 22, 2009 at 05:41:53PM +0300, Pekka Enberg wrote:
> On Thu, Oct 22, 2009 at 5:22 PM, Mel Gorman <mel@xxxxxxxxx> wrote:
> > If a direct reclaim makes no forward progress, it considers whether it
> > should go OOM or not. Whether OOM is triggered or not, it may retry the
> > application afterwards. In times past, this would always wake kswapd as well
> > but currently, kswapd is not woken up after direct reclaim fails. For order-0
> > allocations, this makes little difference but if there is a heavy mix of
> > higher-order allocations that direct reclaim is failing for, it might mean
> > that kswapd is not rewoken for higher orders as much as it did previously.
> >
> > This patch wakes up kswapd when an allocation is being retried after a direct
> > reclaim failure. It would be expected that kswapd is already awake, but
> > this has the effect of telling kswapd to reclaim at the higher order as well.
> >
> > Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
> 
> You seem to have dropped the Reviewed-by tags from me and Christoph
> for this patch.
> 

My apologies. I missed then when going through the old mails.

> >  mm/page_alloc.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index bf72055..dfa4362 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1817,9 +1817,9 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> >        if (NUMA_BUILD && (gfp_mask & GFP_THISNODE) == GFP_THISNODE)
> >                goto nopage;
> >
> > +restart:
> >        wake_all_kswapd(order, zonelist, high_zoneidx);
> >
> > -restart:
> >        /*
> >         * OK, we're below the kswapd watermark and have kicked background
> >         * reclaim. Now things get more complex, so set up alloc_flags according
> > --
> > 1.6.3.3
> >
> > --
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> >
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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