• Keika Kobayashi's avatar
    per-task-delay-accounting: add memory reclaim delay · 873b4771
    Keika Kobayashi authored
    Sometimes, application responses become bad under heavy memory load.
    Applications take a bit time to reclaim memory.  The statistics, how long
    memory reclaim takes, will be useful to measure memory usage.
    
    This patch adds accounting memory reclaim to per-task-delay-accounting for
    accounting the time of do_try_to_free_pages().
    
    <i.e>
    
    - When System is under low memory load,
      memory reclaim may not occur.
    
    $ free
                 total       used       free     shared    buffers     cached
    Mem:       8197800    1577300    6620500          0       4808    1516724
    -/+ buffers/cache:      55768    8142032
    Swap:     16386292          0   16386292
    
    $ vmstat 1
    procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
     r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
     0  0      0 5069748  10612 3014060    0    0     0     0    3   26  0  0 100  0
     0  0      0 5069748  10612 3014060    0    0     0     0    4   22  0  0 100  0
     0  0      0 5069748  10612 3014060    0    0     0     0    3   18  0  0 100  0
    
    Measure the time of tar command.
    
    $ ls -s test.dat
    1501472 test.dat
    
    $ time tar cvf test.tar test.dat
    real    0m13.388s
    user    0m0.116s
    sys     0m5.304s
    
    $ ./delayget -d -p <pid>
    CPU             count     real total  virtual total    delay total
                      428     5528345500     5477116080       62749891
    IO              count    delay total
                      338     8078977189
    SWAP            count    delay total
                        0              0
    RECLAIM         count    delay total
                        0              0
    
    - When system is under heavy memory load
      memory reclaim may occur.
    
    $ vmstat 1
    procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
     r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
     0  0 7159032  49724   1812   3012    0    0     0     0    3   24  0  0 100  0
     0  0 7159032  49724   1812   3012    0    0     0     0    4   24  0  0 100  0
     0  0 7159032  49848   1812   3012    0    0     0     0    3   22  0  0 100  0
    
    In this case, one process uses more 8G memory
    by execution of malloc() and memset().
    
    $ time tar cvf test.tar test.dat
    real    1m38.563s        <-  increased by 85 sec
    user    0m0.140s
    sys     0m7.060s
    
    $ ./delayget -d -p <pid>
    CPU             count     real total  virtual total    delay total
                     9021     7140446250     7315277975      923201824
    IO              count    delay total
                     8965    90466349669
    SWAP            count    delay total
                        3       21036367
    RECLAIM         count    delay total
                      740    61011951153
    
    In the later case, the value of RECLAIM is increasing.
    So, taskstats can show how much memory reclaim influences TAT.
    Signed-off-by: default avatarKeika Kobayashi <kobayashi.kk@ncos.nec.co.jp>
    Acked-by: default avatarBalbir Singh <balbir@linux.vnet.ibm.com>
    Acked-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujistu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    873b4771
delayacct.c 4.74 KB