Commit d9b2ddf8 authored by Naoya Horiguchi's avatar Naoya Horiguchi Committed by Linus Torvalds

tools/vm/page-types.c: avoid memset() in walk_pfn() when count == 1

I found that page-types is very slow and my testing shows many timeout
errors.  Here's an example with a simple program allocating 1000 thps.

  $ time ./page-types -p $(pgrep -f test_alloc)
  ...
  real    0m17.201s
  user    0m16.889s
  sys     0m0.312s

Most of time is spent in memset().  Currently memset() clears over whole
buffer for every walk_pfn() call, which is inefficient when walk_pfn()
is called from walk_vma(), because in that case walk_pfn() is called for
each pfn.  So this patch limits the zero initialization only for the
first element.

  $ time ./page-types.patched -p $(pgrep -f test_alloc)
  ...
  real    0m0.182s
  user    0m0.046s
  sys     0m0.135s

Fixes: 954e95584579 ("tools/vm/page-types.c: add memory cgroup dumping and filtering")
Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Suggested-by: default avatarKonstantin Khlebnikov <koct9i@gmail.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7f2bd006
......@@ -633,6 +633,14 @@ static void walk_pfn(unsigned long voffset,
unsigned long pages;
unsigned long i;
/*
* kpagecgroup_read() reads only if kpagecgroup were opened, but
* /proc/kpagecgroup might even not exist, so it's better to fill
* them with zeros here.
*/
if (count == 1)
cgi[0] = 0;
else
memset(cgi, 0, sizeof cgi);
while (count) {
......
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