From d9b2ddf8078f743729a054362ad96be076f224af Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Thu, 17 Mar 2016 14:20:22 -0700 Subject: 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 --- tools/vm/page-types.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'tools/vm') 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); -- cgit v1.2.3-59-g8ed1b