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. 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>