From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: kosaki.motohiro@jp.fujitsu.com, Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel List <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Rik van Riel <riel@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Minchan Kim <minchan.kim@gmail.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails
Date: Fri, 10 Sep 2010 11:56:59 +0900 (JST) [thread overview]
Message-ID: <20100910115503.C95E.A69D9226@jp.fujitsu.com> (raw)
In-Reply-To: <20100909150558.GB340@csn.ul.ie>
> On Thu, Sep 09, 2010 at 09:32:52AM -0500, Christoph Lameter wrote:
> > On Thu, 9 Sep 2010, Mel Gorman wrote:
> >
> > > > This will have the effect of never sending IPIs for slab allocations since
> > > > they do not do allocations for orders > PAGE_ALLOC_COSTLY_ORDER.
> > > >
> > >
> > > The question is how severe is that? There is somewhat of an expectation
> > > that the lower orders free naturally so it the IPI justified? That said,
> > > our historical behaviour would have looked like
> > >
> > > if (!page && !drained && order) {
> > > drain_all_pages();
> > > draiained = true;
> > > goto retry;
> > > }
> > >
> > > Play it safe for now and go with that?
> >
> > I am fine with no IPIs for order <= COSTLY. Just be aware that this is
> > a change that may have some side effects.
>
> I made the choice consciously. I felt that if slab or slub were depending on
> IPIs to make successful allocations in low-memory conditions that it would
> experience varying stalls on bigger machines due to increased interrupts that
> might be difficult to diagnose while not necessarily improving allocation
> success rates. I also considered that if the machine is under pressure then
> slab and slub may also be releasing pages of the same order and effectively
> recycling their pages without depending on IPIs.
+1.
In these days, average numbers of CPUs are increasing. So we need to be afraid
IPI storm than past.
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next prev parent reply other threads:[~2010-09-10 2:57 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-03 9:08 [PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator V4 Mel Gorman
2010-09-03 9:08 ` [PATCH 1/3] mm: page allocator: Update free page counters after pages are placed on the free list Mel Gorman
2010-09-03 22:38 ` Andrew Morton
2010-09-05 18:06 ` Mel Gorman
2010-09-03 9:08 ` [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake Mel Gorman
2010-09-03 22:55 ` Andrew Morton
2010-09-03 23:17 ` Christoph Lameter
2010-09-03 23:28 ` Andrew Morton
2010-09-04 0:54 ` Christoph Lameter
2010-09-05 18:12 ` Mel Gorman
2010-09-03 9:08 ` [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails Mel Gorman
2010-09-03 23:00 ` Andrew Morton
2010-09-04 2:25 ` Dave Chinner
2010-09-04 3:21 ` Andrew Morton
2010-09-04 7:58 ` Dave Chinner
2010-09-04 8:14 ` Dave Chinner
[not found] ` <20100905015400.GA10714@localhost>
[not found] ` <20100905021555.GG705@dastard>
[not found] ` <20100905060539.GA17450@localhost>
[not found] ` <20100905131447.GJ705@dastard>
2010-09-05 13:45 ` Wu Fengguang
2010-09-05 23:33 ` Dave Chinner
2010-09-06 4:02 ` Dave Chinner
2010-09-06 8:40 ` Mel Gorman
2010-09-06 21:50 ` Dave Chinner
2010-09-08 8:49 ` Dave Chinner
2010-09-09 12:39 ` Mel Gorman
2010-09-10 6:17 ` Dave Chinner
2010-09-07 14:23 ` Christoph Lameter
2010-09-08 2:13 ` Wu Fengguang
2010-09-04 3:23 ` Wu Fengguang
2010-09-04 3:59 ` Andrew Morton
2010-09-04 4:37 ` Wu Fengguang
2010-09-05 18:22 ` Mel Gorman
2010-09-05 18:14 ` Mel Gorman
2010-09-08 7:43 ` KOSAKI Motohiro
2010-09-08 20:05 ` Christoph Lameter
2010-09-09 12:41 ` Mel Gorman
2010-09-09 13:45 ` Christoph Lameter
2010-09-09 13:55 ` Mel Gorman
2010-09-09 14:32 ` Christoph Lameter
2010-09-09 15:05 ` Mel Gorman
2010-09-10 2:56 ` KOSAKI Motohiro [this message]
2010-09-03 23:05 ` [PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator V4 Andrew Morton
2010-09-21 11:17 ` Mel Gorman
2010-09-21 12:58 ` [stable] " Greg KH
2010-09-21 14:23 ` Mel Gorman
2010-09-23 18:49 ` Greg KH
2010-09-24 9:14 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2010-08-31 17:37 [PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator V3 Mel Gorman
2010-08-31 17:37 ` [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails Mel Gorman
2010-08-31 18:26 ` Christoph Lameter
2010-08-23 8:00 [PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator V2 Mel Gorman
2010-08-23 8:00 ` [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails Mel Gorman
2010-08-23 23:17 ` KOSAKI Motohiro
2010-08-16 9:42 [RFC PATCH 0/3] Reduce watermark-related problems with the per-cpu allocator Mel Gorman
2010-08-16 9:42 ` [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails Mel Gorman
2010-08-16 14:50 ` Rik van Riel
2010-08-17 2:57 ` Minchan Kim
2010-08-18 3:02 ` KAMEZAWA Hiroyuki
2010-08-19 14:47 ` Minchan Kim
2010-08-19 15:10 ` Mel Gorman
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