From: Minchan Kim <minchan.kim@gmail.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Arthur Marsh <arthur.marsh@internode.on.net>,
Clemens Ladisch <cladisch@googlemail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] mm: compaction: Minimise the time IRQs are disabled while isolating free pages
Date: Tue, 1 Mar 2011 07:08:07 +0900 [thread overview]
Message-ID: <20110228220807.GA1896@barrios-desktop> (raw)
In-Reply-To: <1298664299-10270-2-git-send-email-mel@csn.ul.ie>
On Fri, Feb 25, 2011 at 08:04:58PM +0000, Mel Gorman wrote:
> compaction_alloc() isolates free pages to be used as migration targets.
> While its scanning, IRQs are disabled on the mistaken assumption the scanning
> should be short. Analysis showed that IRQs were in fact being disabled for
> substantial time. A simple test was run using large anonymous mappings with
> transparent hugepage support enabled to trigger frequent compactions. A
> monitor sampled what the worst IRQ-off latencies were and a post-processing
> tool found the following;
>
> Total sampled time IRQs off (not real total time): 22355
> Event compaction_alloc..compaction_alloc 8409 us count 1
> Event compaction_alloc..compaction_alloc 7341 us count 1
> Event compaction_alloc..compaction_alloc 2463 us count 1
> Event compaction_alloc..compaction_alloc 2054 us count 1
> Event shrink_inactive_list..shrink_zone 1864 us count 1
> Event shrink_inactive_list..shrink_zone 88 us count 1
> Event save_args..call_softirq 36 us count 1
> Event save_args..call_softirq 35 us count 2
> Event __make_request..__blk_run_queue 24 us count 1
> Event __alloc_pages_nodemask..__alloc_pages_nodemask 6 us count 1
>
> i.e. compaction is disabled IRQs for a prolonged period of time - 8ms in
> one instance. The full report generated by the tool can be found at
> http://www.csn.ul.ie/~mel/postings/minfree-20110225/irqsoff-vanilla-micro.report .
> This patch reduces the time IRQs are disabled by simply disabling IRQs
> at the last possible minute. An updated IRQs-off summary report then
> looks like;
>
> Total sampled time IRQs off (not real total time): 5493
> Event shrink_inactive_list..shrink_zone 1596 us count 1
> Event shrink_inactive_list..shrink_zone 1530 us count 1
> Event shrink_inactive_list..shrink_zone 956 us count 1
> Event shrink_inactive_list..shrink_zone 541 us count 1
> Event shrink_inactive_list..shrink_zone 531 us count 1
> Event split_huge_page..add_to_swap 232 us count 1
> Event save_args..call_softirq 36 us count 1
> Event save_args..call_softirq 35 us count 2
> Event __wake_up..__wake_up 1 us count 1
>
> A full report is again available at
> http://www.csn.ul.ie/~mel/postings/minfree-20110225/irqsoff-minimiseirq-free-v1r4-micro.report .
> . As should be obvious, IRQ disabled latencies due to compaction are
> almost elimimnated for this particular test.
>
> [aarcange@redhat.com: Fix initialisation of isolated]
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
--
Kind regards,
Minchan Kim
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next prev parent reply other threads:[~2011-02-28 22:08 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-25 20:04 [PATCH 0/2] Reduce the amount of time compaction disables IRQs for V2 Mel Gorman
2011-02-25 20:04 ` [PATCH 1/2] mm: compaction: Minimise the time IRQs are disabled while isolating free pages Mel Gorman
2011-02-25 22:34 ` Johannes Weiner
2011-02-28 1:55 ` KAMEZAWA Hiroyuki
2011-02-28 22:08 ` Minchan Kim [this message]
2011-02-25 20:04 ` [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration Mel Gorman
2011-02-25 22:32 ` Johannes Weiner
2011-02-26 0:16 ` Andrea Arcangeli
2011-02-28 2:17 ` KAMEZAWA Hiroyuki
2011-02-28 5:48 ` Andrea Arcangeli
2011-02-28 5:54 ` KAMEZAWA Hiroyuki
2011-02-28 9:28 ` Mel Gorman
2011-02-28 9:42 ` KAMEZAWA Hiroyuki
2011-02-28 10:18 ` Mel Gorman
2011-02-28 23:42 ` KAMEZAWA Hiroyuki
2011-03-01 4:11 ` Minchan Kim
2011-03-01 4:49 ` KAMEZAWA Hiroyuki
2011-02-28 23:01 ` Minchan Kim
2011-02-28 23:07 ` Andrea Arcangeli
2011-02-28 23:25 ` Minchan Kim
2011-03-01 22:15 ` Andrew Morton
2011-02-25 20:07 ` [PATCH 0/2] Reduce the amount of time compaction disables IRQs for V2 Andrea Arcangeli
-- strict thread matches above, loose matches on Subject: below --
2011-02-25 18:00 [PATCH 0/2] Reduce the amount of time compaction disables IRQs for Mel Gorman
2011-02-25 18:00 ` [PATCH 1/2] mm: compaction: Minimise the time IRQs are disabled while isolating free pages Mel Gorman
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