Re: [PATCH 4/5] page allocator: Pre-emptively wake kswapd whenhigh-order watermarks are hit

[Tobias Oetiker]

Mel,

Today Mel Gorman wrote:

> On Fri, Oct 23, 2009 at 02:36:53AM -0700, David Rientjes wrote:
> > On Fri, 23 Oct 2009, Mel Gorman wrote:
> >
> > > > Hmm, is this really supposed to be added to __alloc_pages_high_priority()?
> > > > By the patch description I was expecting kswapd to be woken up
> > > > preemptively whenever the preferred zone is below ALLOC_WMARK_LOW and
> > > > we're known to have just allocated at a higher order, not just when
> > > > current was oom killed (when we should already be freeing a _lot_ of
> > > > memory soon) or is doing a higher order allocation during direct reclaim.
> > > >
> > >
> > > It was a somewhat arbitrary choice to have it trigger in the event high
> > > priority allocations were happening frequently.
> > >
> >
> > I don't quite understand, users of PF_MEMALLOC shouldn't be doing these
> > higher order allocations and if ALLOC_NO_WATERMARKS is by way of the oom
> > killer, we should be freeing a substantial amount of memory imminently
> > when it exits that waking up kswapd would be irrelevant.
> >
>
> I agree. I think it's highly unlikely this patch will make any
> difference but I wanted to eliminate it as a possibility. Patch 3 and 4
> were previously one patch that were tested together.

hi hi ... I have tested '3 only' this morning, and the allocation
problems started again ... so for me 3 alone does not work while
3+4 does.

cheers
tobi

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch tobi@xxxxxxxxxx ++41 62 775 9902 / sb: -9900
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