path: root/tools
diff options
authorNaoya Horiguchi <>2016-03-17 14:20:22 -0700
committerLinus Torvalds <>2016-03-17 15:09:34 -0700
commitd9b2ddf8078f743729a054362ad96be076f224af (patch)
treef9117a790718e1262dcd948534f30ebfb683be80 /tools
parent7f2bd006334291178bd2bce3e506d4c7a34a0643 (diff)
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: Naoya Horiguchi <> Suggested-by: Konstantin Khlebnikov <> Cc: Vladimir Davydov <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'tools')
1 files changed, 9 insertions, 1 deletions
diff --git a/tools/vm/page-types.c b/tools/vm/page-types.c
index dab61c377f54..e92903fc7113 100644
--- a/tools/vm/page-types.c
+++ b/tools/vm/page-types.c
@@ -633,7 +633,15 @@ static void walk_pfn(unsigned long voffset,
unsigned long pages;
unsigned long i;
- memset(cgi, 0, sizeof cgi);
+ /*
+ * 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) {
batch = min_t(unsigned long, count, KPAGEFLAGS_BATCH);