From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 363586B0011 for ; Fri, 27 May 2011 01:41:15 -0400 (EDT) Received: from kpbe15.cbf.corp.google.com (kpbe15.cbf.corp.google.com [172.25.105.79]) by smtp-out.google.com with ESMTP id p4R5fBQq000698 for ; Thu, 26 May 2011 22:41:13 -0700 Received: from qyj19 (qyj19.prod.google.com [10.241.83.83]) by kpbe15.cbf.corp.google.com with ESMTP id p4R5eWht006149 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Thu, 26 May 2011 22:41:09 -0700 Received: by qyj19 with SMTP id 19so3118689qyj.9 for ; Thu, 26 May 2011 22:41:07 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1306444069-5094-1-git-send-email-yinghan@google.com> <20110527090506.357698e3.kamezawa.hiroyu@jp.fujitsu.com> <20110527093142.d3733053.kamezawa.hiroyu@jp.fujitsu.com> <20110527111102.f5bd5ff1.kamezawa.hiroyu@jp.fujitsu.com> Date: Thu, 26 May 2011 22:41:07 -0700 Message-ID: Subject: Re: [PATCH] memcg: add pgfault latency histograms From: Ying Han Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro , Minchan Kim , Daisuke Nishimura , Balbir Singh , Tejun Heo , Pavel Emelyanov , Andrew Morton , Li Zefan , Mel Gorman , Christoph Lameter , Johannes Weiner , Rik van Riel , Hugh Dickins , Michal Hocko , Dave Hansen , Zhu Yanhai , "linux-mm@kvack.org" On Thu, May 26, 2011 at 9:45 PM, Ying Han wrote: > On Thu, May 26, 2011 at 7:11 PM, KAMEZAWA Hiroyuki > wrote: >> On Thu, 26 May 2011 18:40:44 -0700 >> Ying Han wrote: >> >>> On Thu, May 26, 2011 at 5:31 PM, KAMEZAWA Hiroyuki >>> wrote: >>> > On Thu, 26 May 2011 17:23:20 -0700 >>> > Ying Han wrote: >>> > >>> >> On Thu, May 26, 2011 at 5:05 PM, KAMEZAWA Hiroyuki < >>> >> kamezawa.hiroyu@jp.fujitsu.com> wrote: >>> >> >>> >> > On Thu, 26 May 2011 14:07:49 -0700 >>> >> > Ying Han wrote: >>> >> > >>> >> > > This adds histogram to capture pagefault latencies on per-memcg = basis. I >>> >> > used >>> >> > > this patch on the memcg background reclaim test, and figured the= re could >>> >> > be more >>> >> > > usecases to monitor/debug application performance. >>> >> > > >>> >> > > The histogram is composed 8 bucket in ns unit. The last one is i= nfinite >>> >> > (inf) >>> >> > > which is everything beyond the last one. To be more flexible, th= e buckets >>> >> > can >>> >> > > be reset and also each bucket is configurable at runtime. >>> >> > > >>> >> > > memory.pgfault_histogram: exports the histogram on per-memcg bas= is and >>> >> > also can >>> >> > > be reset by echoing "reset". Meantime, all the buckets are writa= ble by >>> >> > echoing >>> >> > > the range into the API. see the example below. >>> >> > > >>> >> > > /proc/sys/vm/pgfault_histogram: the global sysfs tunablecan be u= sed to >>> >> > turn >>> >> > > on/off recording the histogram. >>> >> > > >>> >> > > Functional Test: >>> >> > > Create a memcg with 10g hard_limit, running dd & allocate 8g ano= n page. >>> >> > > Measure the anon page allocation latency. >>> >> > > >>> >> > > $ mkdir /dev/cgroup/memory/B >>> >> > > $ echo 10g >/dev/cgroup/memory/B/memory.limit_in_bytes >>> >> > > $ echo $$ >/dev/cgroup/memory/B/tasks >>> >> > > $ dd if=3D/dev/zero of=3D/export/hdc3/dd/tf0 bs=3D1024 count=3D2= 0971520 & >>> >> > > $ allocate 8g anon pages >>> >> > > >>> >> > > $ echo 1 >/proc/sys/vm/pgfault_histogram >>> >> > > >>> >> > > $ cat /dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > pgfault latency histogram (ns): >>> >> > > < 600 =A0 =A0 =A0 =A0 =A0 =A02051273 >>> >> > > < 1200 =A0 =A0 =A0 =A0 =A0 40859 >>> >> > > < 2400 =A0 =A0 =A0 =A0 =A0 4004 >>> >> > > < 4800 =A0 =A0 =A0 =A0 =A0 1605 >>> >> > > < 9600 =A0 =A0 =A0 =A0 =A0 170 >>> >> > > < 19200 =A0 =A0 =A0 =A0 =A082 >>> >> > > < 38400 =A0 =A0 =A0 =A0 =A06 >>> >> > > < inf =A0 =A0 =A0 =A0 =A0 =A00 >>> >> > > >>> >> > > $ echo reset >/dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > $ cat /dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > pgfault latency histogram (ns): >>> >> > > < 600 =A0 =A0 =A0 =A0 =A0 =A00 >>> >> > > < 1200 =A0 =A0 =A0 =A0 =A0 0 >>> >> > > < 2400 =A0 =A0 =A0 =A0 =A0 0 >>> >> > > < 4800 =A0 =A0 =A0 =A0 =A0 0 >>> >> > > < 9600 =A0 =A0 =A0 =A0 =A0 0 >>> >> > > < 19200 =A0 =A0 =A0 =A0 =A00 >>> >> > > < 38400 =A0 =A0 =A0 =A0 =A00 >>> >> > > < inf =A0 =A0 =A0 =A0 =A0 =A00 >>> >> > > >>> >> > > $ echo 500 520 540 580 600 1000 5000 >>> >> > >/dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > $ cat /dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > pgfault latency histogram (ns): >>> >> > > < 500 =A0 =A0 =A0 =A0 =A0 =A050 >>> >> > > < 520 =A0 =A0 =A0 =A0 =A0 =A0151 >>> >> > > < 540 =A0 =A0 =A0 =A0 =A0 =A03715 >>> >> > > < 580 =A0 =A0 =A0 =A0 =A0 =A01859812 >>> >> > > < 600 =A0 =A0 =A0 =A0 =A0 =A0202241 >>> >> > > < 1000 =A0 =A0 =A0 =A0 =A0 25394 >>> >> > > < 5000 =A0 =A0 =A0 =A0 =A0 5875 >>> >> > > < inf =A0 =A0 =A0 =A0 =A0 =A0186 >>> >> > > >>> >> > > Performance Test: >>> >> > > I ran through the PageFaultTest (pft) benchmark to measure the o= verhead >>> >> > of >>> >> > > recording the histogram. There is no overhead observed on both >>> >> > "flt/cpu/s" >>> >> > > and "fault/wsec". >>> >> > > >>> >> > > $ mkdir /dev/cgroup/memory/A >>> >> > > $ echo 16g >/dev/cgroup/memory/A/memory.limit_in_bytes >>> >> > > $ echo $$ >/dev/cgroup/memory/A/tasks >>> >> > > $ ./pft -m 15g -t 8 -T a >>> >> > > >>> >> > > Result: >>> >> > > "fault/wsec" >>> >> > > >>> >> > > $ ./ministat no_histogram histogram >>> >> > > x no_histogram >>> >> > > + histogram >>> >> > > >>> >> > +-----------------------------------------------------------------= ---------+ >>> >> > > =A0 =A0N =A0 =A0 =A0 =A0 =A0 Min =A0 =A0 =A0 =A0 =A0 Max =A0 =A0= =A0 =A0Median =A0 =A0 =A0 =A0 =A0 Avg >>> >> > =A0Stddev >>> >> > > x =A0 5 =A0 =A0 813404.51 =A0 =A0 824574.98 =A0 =A0 =A0821661.3 = =A0 =A0 820470.83 >>> >> > 4202.0758 >>> >> > > + =A0 5 =A0 =A0 821228.91 =A0 =A0 825894.66 =A0 =A0 822874.65 = =A0 =A0 823374.15 >>> >> > 1787.9355 >>> >> > > >>> >> > > "flt/cpu/s" >>> >> > > >>> >> > > $ ./ministat no_histogram histogram >>> >> > > x no_histogram >>> >> > > + histogram >>> >> > > >>> >> > +-----------------------------------------------------------------= ---------+ >>> >> > > =A0 =A0N =A0 =A0 =A0 =A0 =A0 Min =A0 =A0 =A0 =A0 =A0 Max =A0 =A0= =A0 =A0Median =A0 =A0 =A0 =A0 =A0 Avg >>> >> > =A0Stddev >>> >> > > x =A0 5 =A0 =A0 104951.93 =A0 =A0 106173.13 =A0 =A0 105142.73 = =A0 =A0 =A0105349.2 >>> >> > 513.78158 >>> >> > > + =A0 5 =A0 =A0 104697.67 =A0 =A0 =A0105416.1 =A0 =A0 104943.52 = =A0 =A0 104973.77 >>> >> > 269.24781 >>> >> > > No difference proven at 95.0% confidence >>> >> > > >>> >> > > Signed-off-by: Ying Han >>> >> > >>> >> > Hmm, interesting....but isn't it very very very complicated interf= ace ? >>> >> > Could you make this for 'perf' ? Then, everyone (including someone= who >>> >> > don't use memcg) >>> >> > will be happy. >>> >> > >>> >> >>> >> Thank you for looking at it. >>> >> >>> >> There is only one per-memcg API added which is basically exporting t= he >>> >> histogram. The "reset" and reconfiguring the bucket is not "must" bu= t make >>> >> it more flexible. Also, the sysfs API can be reduced if necessary si= nce >>> >> there is no over-head observed by always turning it on anyway. >>> >> >>> >> I am not familiar w/ perf, any suggestions how it is supposed to be = look >>> >> like? >>> >> >>> >> Thanks >>> >> >>> > >>> > IIUC, you can record "all" latency information by perf record. Then, = latency >>> > information can be dumped out to some file. >>> > >>> > You can add a python? script for perf as >>> > >>> > =A0# perf report memory-reclaim-latency-histgram -f perf.data >>> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0-o 500,1000,1500,2000..... >>> > =A0 ...show histgram in text.. or report the histgram in graphic. >>> > >>> > Good point is >>> > =A0- you can reuse perf.data and show histgram from another point of = view. >>> > >>> > =A0- you can show another cut of view, for example, I think you can w= rite a >>> > =A0 =A0parser to show "changes in hisgram by time", easily. >>> > =A0 =A0You may able to generate a movie ;) >>> > >>> > =A0- Now, perf cgroup is supported. Then, >>> > =A0 =A0- you can see per task histgram >>> > =A0 =A0- you can see per cgroup histgram >>> > =A0 =A0- you can see per system-wide histgram >>> > =A0 =A0 =A0(If you record latency of usual kswapd/alloc_pages) >>> > >>> > =A0- If you record latency within shrink_zone(), you can show per-zon= e >>> > =A0 =A0reclaim latency histgram. record parsers can gather them and >>> > =A0 =A0show histgram. This will be benefical to cpuset users. >>> > >>> > >>> > I'm sorry if I miss something. >>> >>> After study a bit on perf, it is not feasible in this casecase. The >>> cpu & memory overhead of perf is overwhelming.... Each page fault will >>> generate a record in the buffer and how many data we can record in the >>> buffer, and how many data will be processed later.. Most of the data >>> that is recorded by the general perf framework is not needed here. >>> >> >> I disagree. "each page fault" is not correct. "every lru scan" is correc= t. >> Then, record to buffer will be at most memory.failcnt times. > > Hmm. Sorry I might miss something here... :( > > The page fault histogram recorded is per page-fault, only the ones > trigger reclaim. typo. I meant it is recording per page-fault, not only the one triggering the reclaim. --Ying The background reclaim testing is just one usecase of > it, and we need this information for more > general usage to monitor application performance. So i recorded the > latency for each single page fault. > > --Ying > >> >> please consider more. >> >> >> Thanks, >> -Kame >> >> > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org