On Thu, May 26, 2011 at 9:45 PM, Ying Han <yinghan@xxxxxxxxxx> wrote: > On Thu, May 26, 2011 at 7:11 PM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: >> On Thu, 26 May 2011 18:40:44 -0700 >> Ying Han <yinghan@xxxxxxxxxx> wrote: >> >>> On Thu, May 26, 2011 at 5:31 PM, KAMEZAWA Hiroyuki >>> <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: >>> > On Thu, 26 May 2011 17:23:20 -0700 >>> > Ying Han <yinghan@xxxxxxxxxx> wrote: >>> > >>> >> On Thu, May 26, 2011 at 5:05 PM, KAMEZAWA Hiroyuki < >>> >> kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: >>> >> >>> >> > On Thu, 26 May 2011 14:07:49 -0700 >>> >> > Ying Han <yinghan@xxxxxxxxxx> wrote: >>> >> > >>> >> > > This adds histogram to capture pagefault latencies on per-memcg basis. I >>> >> > used >>> >> > > this patch on the memcg background reclaim test, and figured there could >>> >> > be more >>> >> > > usecases to monitor/debug application performance. >>> >> > > >>> >> > > The histogram is composed 8 bucket in ns unit. The last one is infinite >>> >> > (inf) >>> >> > > which is everything beyond the last one. To be more flexible, the buckets >>> >> > can >>> >> > > be reset and also each bucket is configurable at runtime. >>> >> > > >>> >> > > memory.pgfault_histogram: exports the histogram on per-memcg basis and >>> >> > also can >>> >> > > be reset by echoing "reset". Meantime, all the buckets are writable by >>> >> > echoing >>> >> > > the range into the API. see the example below. >>> >> > > >>> >> > > /proc/sys/vm/pgfault_histogram: the global sysfs tunablecan be used to >>> >> > turn >>> >> > > on/off recording the histogram. >>> >> > > >>> >> > > Functional Test: >>> >> > > Create a memcg with 10g hard_limit, running dd & allocate 8g anon page. >>> >> > > Measure the anon page allocation latency. >>> >> > > >>> >> > > $ mkdir /dev/cgroup/memory/B >>> >> > > $ echo 10g >/dev/cgroup/memory/B/memory.limit_in_bytes >>> >> > > $ echo $$ >/dev/cgroup/memory/B/tasks >>> >> > > $ dd if=/dev/zero of=/export/hdc3/dd/tf0 bs=1024 count=20971520 & >>> >> > > $ allocate 8g anon pages >>> >> > > >>> >> > > $ echo 1 >/proc/sys/vm/pgfault_histogram >>> >> > > >>> >> > > $ cat /dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > pgfault latency histogram (ns): >>> >> > > < 600 2051273 >>> >> > > < 1200 40859 >>> >> > > < 2400 4004 >>> >> > > < 4800 1605 >>> >> > > < 9600 170 >>> >> > > < 19200 82 >>> >> > > < 38400 6 >>> >> > > < inf 0 >>> >> > > >>> >> > > $ echo reset >/dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > $ cat /dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > pgfault latency histogram (ns): >>> >> > > < 600 0 >>> >> > > < 1200 0 >>> >> > > < 2400 0 >>> >> > > < 4800 0 >>> >> > > < 9600 0 >>> >> > > < 19200 0 >>> >> > > < 38400 0 >>> >> > > < inf 0 >>> >> > > >>> >> > > $ echo 500 520 540 580 600 1000 5000 >>> >> > >/dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > $ cat /dev/cgroup/memory/B/memory.pgfault_histogram >>> >> > > pgfault latency histogram (ns): >>> >> > > < 500 50 >>> >> > > < 520 151 >>> >> > > < 540 3715 >>> >> > > < 580 1859812 >>> >> > > < 600 202241 >>> >> > > < 1000 25394 >>> >> > > < 5000 5875 >>> >> > > < inf 186 >>> >> > > >>> >> > > Performance Test: >>> >> > > I ran through the PageFaultTest (pft) benchmark to measure the overhead >>> >> > of >>> >> > > recording the histogram. There is no overhead observed on both >>> >> > "flt/cpu/s" >>> >> > > and "fault/wsec". >>> >> > > >>> >> > > $ mkdir /dev/cgroup/memory/A >>> >> > > $ echo 16g >/dev/cgroup/memory/A/memory.limit_in_bytes >>> >> > > $ echo $$ >/dev/cgroup/memory/A/tasks >>> >> > > $ ./pft -m 15g -t 8 -T a >>> >> > > >>> >> > > Result: >>> >> > > "fault/wsec" >>> >> > > >>> >> > > $ ./ministat no_histogram histogram >>> >> > > x no_histogram >>> >> > > + histogram >>> >> > > >>> >> > +--------------------------------------------------------------------------+ >>> >> > > N Min Max Median Avg >>> >> > Stddev >>> >> > > x 5 813404.51 824574.98 821661.3 820470.83 >>> >> > 4202.0758 >>> >> > > + 5 821228.91 825894.66 822874.65 823374.15 >>> >> > 1787.9355 >>> >> > > >>> >> > > "flt/cpu/s" >>> >> > > >>> >> > > $ ./ministat no_histogram histogram >>> >> > > x no_histogram >>> >> > > + histogram >>> >> > > >>> >> > +--------------------------------------------------------------------------+ >>> >> > > N Min Max Median Avg >>> >> > Stddev >>> >> > > x 5 104951.93 106173.13 105142.73 105349.2 >>> >> > 513.78158 >>> >> > > + 5 104697.67 105416.1 104943.52 104973.77 >>> >> > 269.24781 >>> >> > > No difference proven at 95.0% confidence >>> >> > > >>> >> > > Signed-off-by: Ying Han <yinghan@xxxxxxxxxx> >>> >> > >>> >> > Hmm, interesting....but isn't it very very very complicated interface ? >>> >> > 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 the >>> >> histogram. The "reset" and reconfiguring the bucket is not "must" but make >>> >> it more flexible. Also, the sysfs API can be reduced if necessary since >>> >> 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 >>> > >>> > # perf report memory-reclaim-latency-histgram -f perf.data >>> > -o 500,1000,1500,2000..... >>> > ...show histgram in text.. or report the histgram in graphic. >>> > >>> > Good point is >>> > - you can reuse perf.data and show histgram from another point of view. >>> > >>> > - you can show another cut of view, for example, I think you can write a >>> > parser to show "changes in hisgram by time", easily. >>> > You may able to generate a movie ;) >>> > >>> > - Now, perf cgroup is supported. Then, >>> > - you can see per task histgram >>> > - you can see per cgroup histgram >>> > - you can see per system-wide histgram >>> > (If you record latency of usual kswapd/alloc_pages) >>> > >>> > - If you record latency within shrink_zone(), you can show per-zone >>> > reclaim latency histgram. record parsers can gather them and >>> > show 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 correct. >> 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@xxxxxxxxxx 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: <a href