* Ying Han <yinghan@xxxxxxxxxx> [2011-05-26 14:07:49]: > 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. > inf is a bit confusing for page faults -- no? Why not call it "rest" or something line "> 38400". BTW, why was 600 used as base? > 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. > Why not make this per memcg? > 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 Can't we use something like "-1" to mean reset? -- Three Cheers, Balbir -- 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>