lkml.org 
[lkml]   [2011]   [May]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 0/8] memcg async reclaim v2
    On Mon, 23 May 2011 15:38:31 -0700
    Ying Han <yinghan@google.com> wrote:

    > Hi Kame:
    >
    > I applied and tested the patchset on top of mmotm-2011-05-12-15-52. I
    > admit that I didn't look the patch closely yet, which I plan to do
    > next. Now i have few quick questions based on the testing result:
    >
    > Test:
    > 1) create a 2g memcg and enable async_control
    > $ mkdir /dev/cgroup/memory/A
    > $ echo 2g >/dev/cgroup/memory/A/memory.limit_in_bytes
    > $ echo 1 >/dev/cgroup/memory/A/memory.async_control
    >
    > 2) read a 20g file in the memcg
    > $ echo $$ >/dev/cgroup/memory/A/tasks
    > $ time cat /export/hdc3/dd_A/tf0 > /dev/zero
    >
    > real 4m26.677s
    > user 0m0.222s
    > sys 0m28.481s
    >
    > Here are the questions:
    >
    > 1. I monitored the "top" while the test is running. The amount of
    > cputime the kworkers take worries me, and the following top output
    > stays pretty consistent while the "cat" is running/
    >

    memcg-async's kworker is kworker/u:x .....because of UNBOUND_WQ.
    Then, kworker you see is for other purpose....Hmm, from trace log,
    most of them are for "draining" per-cpu memcg cache. I'll prepare a patch.




    > Tasks: 152 total, 2 running, 150 sleeping, 0 stopped, 0 zombie
    > Cpu(s): 0.1%us, 1.2%sy, 0.0%ni, 87.6%id, 10.6%wa, 0.0%hi, 0.5%si, 0.0%st
    > Mem: 32963480k total, 2694728k used, 30268752k free, 3888k buffers
    > Swap: 0k total, 0k used, 0k free, 2316500k cached
    >
    > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    > 389 root 20 0 0 0 0 R 45 0.0 1:36.24
    > kworker/3:1
    > 23127 root 20 0 0 0 0 S 44 0.0 0:13.44
    > kworker/4:2
    > 393 root 20 0 0 0 0 S 43 0.0 2:02.28
    > kworker/7:1
    > 32 root 20 0 0 0 0 S 42 0.0 1:54.02
    > kworker/6:0
    > 1230 root 20 0 0 0 0 S 42 0.0 1:22.01
    > kworker/2:2
    > 23130 root 20 0 0 0 0 S 31 0.0 0:04.04
    > kworker/0:2
    > 391 root 20 0 0 0 0 S 22 0.0 1:45.79
    > kworker/5:1
    > 23109 root 20 0 3104 228 180 D 10 0.0 0:08.56 cat
    >
    > I attached the tracing output of the kworkers while they are running
    > by doing the following:
    >
    > $ mount -t debugfs nodev /sys/kernel/debug/
    > $ echo workqueue:workqueue_queue_work > /sys/kernel/debug/tracing/set_event
    > $ cat /sys/kernel/debug/tracing/trace_pipe > out.txt
    >
    > 2. I can not justify the cputime on the kworkers. I am looking for the
    > patch which we exports the time before and after workitem on memcg
    > basis. I recall we have that in previous post, sorry I missed that
    > patch somehere.
    >
    > # cat /cgroup/memory/A/memory.stat
    > ....
    > direct_elapsed_ns 0
    > wmark_elapsed_ns 103566424
    > direct_scanned 0
    > wmark_scanned 29303
    > direct_freed 0
    > wmark_freed 29290
    >

    I didn't include this for this version because you and others working on
    memory.stat file. I wanted to avoid to add new mess ;)
    I'll include it again in v3.



    > 3. Here is the outout of memory.stat after the test, the last one is
    > the memory.failcnt. As far as I remember, the failcnt is far higher
    > than the result i got on previous testing (per-memcg-per-kswapd
    > patch). This is all clean file pages which shouldn't be hard to
    > reclaim.
    >
    > cache 2147151872
    > rss 94208
    > mapped_file 0
    > pgpgin 5242945
    > pgpgout 4718715
    > pgfault 274
    > pgmajfault 0
    > 1050041
    >
    > Please let me know if the current version isn't ready for testing, and
    > I will wait :)
    >

    This version has tweaked to be less cpu hogging than previous one. So,
    hit_limit increases. I'll drop some tweakes I added in v2 for starting from
    a simple one.

    I'll post v3 in this week. But if dirty_ratio is ready, I think it should be
    merged 1st. But it's merge window....

    Thanks,
    -Kame






    \
     
     \ /
      Last update: 2011-05-24 02:29    [W:0.036 / U:29.972 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site