• Andrei Vagin's avatar
    proc: add seq_put_decimal_ull_width to speed up /proc/pid/smaps · d1be35cb
    Andrei Vagin authored
    seq_put_decimal_ull_w(m, str, val, width) prints a decimal number with a
    specified minimal field width.
    
    It is equivalent of seq_printf(m, "%s%*d", str, width, val), but it
    works much faster.
    
    == test_smaps.py
      num = 0
      with open("/proc/1/smaps") as f:
              for x in xrange(10000):
                      data = f.read()
                      f.seek(0, 0)
    ==
    
    == Before patch ==
      $ time python test_smaps.py
      real    0m4.593s
      user    0m0.398s
      sys     0m4.158s
    
    == After patch ==
      $ time python test_smaps.py
      real    0m3.828s
      user    0m0.413s
      sys     0m3.408s
    
    $ perf -g record python test_smaps.py
    == Before patch ==
    -   79.01%     3.36%  python   [kernel.kallsyms]    [k] show_smap.isra.33
       - 75.65% show_smap.isra.33
          + 48.85% seq_printf
          + 15.75% __walk_page_range
          + 9.70% show_map_vma.isra.23
            0.61% seq_puts
    
    == After patch ==
    -   75.51%     4.62%  python   [kernel.kallsyms]    [k] show_smap.isra.33
       - 70.88% show_smap.isra.33
          + 24.82% seq_put_decimal_ull_w
          + 19.78% __walk_page_range
          + 12.74% seq_printf
          + 11.08% show_map_vma.isra.23
          + 1.68% seq_puts
    
    [akpm@linux-foundation.org: fix drivers/of/unittest.c build]
    Link: http://lkml.kernel.org/r/20180212074931.7227-1-avagin@openvz.orgSigned-off-by: default avatarAndrei Vagin <avagin@openvz.org>
    Cc: Alexey Dobriyan <adobriyan@gmail.com>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    d1be35cb
seq_file.c 24.4 KB