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Message-Id: <20110527114837.8fae7f00.kamezawa.hiroyu@jp.fujitsu.com> Date: Fri, 27 May 2011 11:48:37 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: Ying Han <yinghan@...gle.com> Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>, "balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com> Subject: Re: [RFC][PATCH v3 0/10] memcg async reclaim On Thu, 26 May 2011 18:49:26 -0700 Ying Han <yinghan@...gle.com> wrote: > On Wed, May 25, 2011 at 10:10 PM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@...fujitsu.com> wrote: > > > > It's now merge window...I just dump my patch queue to hear other's idea. > > I wonder I should wait until dirty_ratio for memcg is queued to mmotm... > > I'll be busy with LinuxCon Japan etc...in the next week. > > > > This patch is onto mmotm-May-11 + some patches queued in mmotm, as numa_stat. > > > > This is a patch for memcg to keep margin to the limit in background. > > By keeping some margin to the limit in background, application can > > avoid foreground memory reclaim at charge() and this will help latency. > > > > Main changes from v2 is. > > - use SCHED_IDLE. > > - removed most of heuristic codes. Now, code is very simple. > > > > By using SCHED_IDLE, async memory reclaim can only consume 0.3%? of cpu > > if the system is truely busy but can use much CPU if the cpu is idle. > > Because my purpose is for reducing latency without affecting other running > > applications, SCHED_IDLE fits this work. > > > > If application need to stop by some I/O or event, background memory reclaim > > will cull memory while the system is idle. > > > > Perforemce: > > Running an httpd (apache) under 300M limit. And access 600MB working set > > with normalized distribution access by apatch-bench. > > apatch bench's concurrency was 4 and did 40960 accesses. > > > > Without async reclaim: > > Connection Times (ms) > > min mean[+/-sd] median max > > Connect: 0 0 0.0 0 2 > > Processing: 30 37 28.3 32 1793 > > Waiting: 28 35 25.5 31 1792 > > Total: 30 37 28.4 32 1793 > > > > Percentage of the requests served within a certain time (ms) > > 50% 32 > > 66% 32 > > 75% 33 > > 80% 34 > > 90% 39 > > 95% 60 > > 98% 100 > > 99% 133 > > 100% 1793 (longest request) > > > > With async reclaim: > > Connection Times (ms) > > min mean[+/-sd] median max > > Connect: 0 0 0.0 0 2 > > Processing: 30 35 12.3 32 678 > > Waiting: 28 34 12.0 31 658 > > Total: 30 35 12.3 32 678 > > > > Percentage of the requests served within a certain time (ms) > > 50% 32 > > 66% 32 > > 75% 33 > > 80% 34 > > 90% 39 > > 95% 49 > > 98% 71 > > 99% 86 > > 100% 678 (longest request) > > > > > > It seems latency is stabilized by hiding memory reclaim. > > > > The score for memory reclaim was following. > > See patch 10 for meaning of each member. > > > > == without async reclaim == > > recent_scan_success_ratio 44 > > limit_scan_pages 388463 > > limit_freed_pages 162238 > > limit_elapsed_ns 13852159231 > > soft_scan_pages 0 > > soft_freed_pages 0 > > soft_elapsed_ns 0 > > margin_scan_pages 0 > > margin_freed_pages 0 > > margin_elapsed_ns 0 > > > > == with async reclaim == > > recent_scan_success_ratio 6 > > limit_scan_pages 0 > > limit_freed_pages 0 > > limit_elapsed_ns 0 > > soft_scan_pages 0 > > soft_freed_pages 0 > > soft_elapsed_ns 0 > > margin_scan_pages 1295556 > > margin_freed_pages 122450 > > margin_elapsed_ns 644881521 > > > > > > For this case, SCHED_IDLE workqueue can reclaim enough memory to the httpd. > > > > I may need to dig why scan_success_ratio is far different in the both case. > > I guess the difference of epalsed_ns is because several threads enter > > memory reclaim when async reclaim doesn't run. But may not... > > > > > Hmm.. I noticed a very strange behavior on a simple test w/ the patch set. > > Test: > I created a 4g memcg and start doing cat. Then the memcg being OOM > killed as soon as it reaches its hard_limit. We shouldn't hit OOM even > w/o async-reclaim. > > Again, I will read through the patch. But like to post the test result first. > > $ echo $$ >/dev/cgroup/memory/A/tasks > $ cat /dev/cgroup/memory/A/memory.limit_in_bytes > 4294967296 > > $ time cat /export/hdc3/dd_A/tf0 > /dev/zero > Killed > > real 0m53.565s > user 0m0.061s > sys 0m4.814s > Hmm, what I see is == root@...extal kamezawa]# ls -l test/1G -rw-rw-r--. 1 kamezawa kamezawa 1053261824 May 13 13:58 test/1G [root@...extal kamezawa]# mkdir /cgroup/memory/A [root@...extal kamezawa]# echo 0 > /cgroup/memory/A/tasks [root@...extal kamezawa]# echo 300M > /cgroup/memory/A/memory.limit_in_bytes [root@...extal kamezawa]# echo 1 > /cgroup/memory/A/memory.async_control [root@...extal kamezawa]# cat test/1G > /dev/null [root@...extal kamezawa]# cat /cgroup/memory/A/memory.reclaim_stat recent_scan_success_ratio 83 limit_scan_pages 82 limit_freed_pages 49 limit_elapsed_ns 242507 soft_scan_pages 0 soft_freed_pages 0 soft_elapsed_ns 0 margin_scan_pages 218630 margin_freed_pages 181598 margin_elapsed_ns 117466604 [root@...extal kamezawa]# == I'll turn off swapaccount and try again. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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