• Ganesh Mahendran's avatar
    mm/zsmalloc: add statistics support · 0f050d99
    Ganesh Mahendran authored
    Keeping fragmentation of zsmalloc in a low level is our target.  But now
    we still need to add the debug code in zsmalloc to get the quantitative
    data.
    
    This patch adds a new configuration CONFIG_ZSMALLOC_STAT to enable the
    statistics collection for developers.  Currently only the objects
    statatitics in each class are collected.  User can get the information via
    debugfs.
    
         cat /sys/kernel/debug/zsmalloc/zram0/...
    
    For example:
    
    After I copied "jdk-8u25-linux-x64.tar.gz" to zram with ext4 filesystem:
     class  size obj_allocated   obj_used pages_used
         0    32             0          0          0
         1    48           256         12          3
         2    64            64         14          1
         3    80            51          7          1
         4    96           128          5          3
         5   112            73          5          2
         6   128            32          4          1
         7   144             0          0          0
         8   160             0          0          0
         9   176             0          0          0
        10   192             0          0          0
        11   208             0          0          0
        12   224             0          0          0
        13   240             0          0          0
        14   256            16          1          1
        15   272            15          9          1
        16   288             0          0          0
        17   304             0          0          0
        18   320             0          0          0
        19   336             0          0          0
        20   352             0          0          0
        21   368             0          0          0
        22   384             0          0          0
        23   400             0          0          0
        24   416             0          0          0
        25   432             0          0          0
        26   448             0          0          0
        27   464             0          0          0
        28   480             0          0          0
        29   496            33          1          4
        30   512             0          0          0
        31   528             0          0          0
        32   544             0          0          0
        33   560             0          0          0
        34   576             0          0          0
        35   592             0          0          0
        36   608             0          0          0
        37   624             0          0          0
        38   640             0          0          0
        40   672             0          0          0
        42   704             0          0          0
        43   720            17          1          3
        44   736             0          0          0
        46   768             0          0          0
        49   816             0          0          0
        51   848             0          0          0
        52   864            14          1          3
        54   896             0          0          0
        57   944            13          1          3
        58   960             0          0          0
        62  1024             4          1          1
        66  1088            15          2          4
        67  1104             0          0          0
        71  1168             0          0          0
        74  1216             0          0          0
        76  1248             0          0          0
        83  1360             3          1          1
        91  1488            11          1          4
        94  1536             0          0          0
       100  1632             5          1          2
       107  1744             0          0          0
       111  1808             9          1          4
       126  2048             4          4          2
       144  2336             7          3          4
       151  2448             0          0          0
       168  2720            15         15         10
       190  3072            28         27         21
       202  3264             0          0          0
       254  4096         36209      36209      36209
    
     Total               37022      36326      36288
    
    We can calculate the overall fragentation by the last line:
        Total               37022      36326      36288
        (37022 - 36326) / 37022 = 1.87%
    
    Also by analysing objects alocated in every class we know why we got so
    low fragmentation: Most of the allocated objects is in <class 254>.  And
    there is only 1 page in class 254 zspage.  So, No fragmentation will be
    introduced by allocating objs in class 254.
    
    And in future, we can collect other zsmalloc statistics as we need and
    analyse them.
    Signed-off-by: 's avatarGanesh Mahendran <opensource.ganesh@gmail.com>
    Suggested-by: 's avatarMinchan Kim <minchan@kernel.org>
    Acked-by: 's avatarMinchan Kim <minchan@kernel.org>
    Cc: Nitin Gupta <ngupta@vflare.org>
    Cc: Seth Jennings <sjennings@variantweb.net>
    Cc: Dan Streetman <ddstreet@ieee.org>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    0f050d99
zsmalloc.c 36.5 KB