From: Andrew Morton <akpm@linux-foundation.org>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: linux-mm@kvack.org, linaro-mm-sig@lists.linaro.org,
linux-kernel@vger.kernel.org,
Kyungmin Park <kyungmin.park@samsung.com>,
Mel Gorman <mel@csn.ul.ie>, Michal Nazarewicz <mina86@mina86.com>,
Minchan Kim <minchan@kernel.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH] mm: cma: allocate pages from CMA if NR_FREE_PAGES approaches low water mark
Date: Mon, 19 Nov 2012 12:43:27 -0800 [thread overview]
Message-ID: <20121119124327.20e008a0.akpm@linux-foundation.org> (raw)
In-Reply-To: <50AA526A.7080505@samsung.com>
On Mon, 19 Nov 2012 16:38:18 +0100
Marek Szyprowski <m.szyprowski@samsung.com> wrote:
> Hello,
>
> On 11/14/2012 11:58 PM, Andrew Morton wrote:
> > On Mon, 12 Nov 2012 09:59:42 +0100
> > Marek Szyprowski <m.szyprowski@samsung.com> wrote:
> >
> > > It has been observed that system tends to keep a lot of CMA free pages
> > > even in very high memory pressure use cases. The CMA fallback for movable
> > > pages is used very rarely, only when system is completely pruned from
> > > MOVABLE pages, what usually means that the out-of-memory even will be
> > > triggered very soon. To avoid such situation and make better use of CMA
> > > pages, a heuristics is introduced which turns on CMA fallback for movable
> > > pages when the real number of free pages (excluding CMA free pages)
> > > approaches low water mark.
>
> ...
>
> > erk, this is right on the page allocator hotpath. Bad.
>
> Yes, I know that it adds an overhead to allocation hot path, but I found
> no other
> place for such change. Do You have any suggestion where such change can
> be applied
> to avoid additional load on hot path?
Do the work somewhere else, not on a hot path? Somewhere on the page
reclaim path sounds appropriate. How messy would it be to perform some
sort of balancing at reclaim time?
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next prev parent reply other threads:[~2012-11-19 20:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-12 8:59 [PATCH] mm: cma: allocate pages from CMA if NR_FREE_PAGES approaches low water mark Marek Szyprowski
2012-11-14 22:58 ` Andrew Morton
2012-11-19 15:38 ` Marek Szyprowski
2012-11-19 20:43 ` Andrew Morton [this message]
2012-11-20 0:01 ` Minchan Kim
2012-11-20 14:49 ` Marek Szyprowski
2012-11-20 15:41 ` Michal Nazarewicz
2012-11-21 1:05 ` Minchan Kim
2012-11-21 13:07 ` Michal Nazarewicz
2012-11-21 13:25 ` Minchan Kim
2012-11-21 15:50 ` Marek Szyprowski
2012-11-23 4:42 ` Minchan Kim
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