On Wed, Mar 09, 2016 at 07:28:21AM +0300, Konstantin Khlebnikov wrote: > On Tue, Mar 8, 2016 at 8:58 AM, Naoya Horiguchi > <n-horiguchi@xxxxxxxxxxxxx> wrote: > > On Tue, Mar 08, 2016 at 08:12:09AM +0300, Konstantin Khlebnikov wrote: > >> On Tue, Mar 8, 2016 at 4:47 AM, Naoya Horiguchi > >> <n-horiguchi@xxxxxxxxxxxxx> wrote: > >> > 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 > >> > > >> > $ time ./page-types.patched -p $(pgrep -f test_alloc) > >> > ... > >> > real 0m0.182s > >> > user 0m0.046s > >> > sys 0m0.135s > >> > > >> > Most of time is spent in memset(), which isn't necessary because we check > >> > that the return of kpagecgroup_read() is equal to pages and uninitialized > >> > memory is never used. So we can drop this memset(). > >> > >> These zeros are used in show_page_range() - for merging pages into ranges. > > > > Hi Konstantin, > > > > Thank you for the response. The below code does solve the problem, so that's fine. > > > > But I don't understand how the zeros are used. show_page_range() is called > > via add_page() which is called for i=0 to i=pages-1, and the buffer cgi is > > already filled for the range [i, pages-1] by kpagecgroup_read(), so even if > > without zero initialization, kpagecgroup_read() properly fills zeros, right? > > IOW, is there any problem if we don't do this zero initialization? > > kpagecgroup_read() reads only if kpagecgroup were opened, > /proc/kpagecgroup might even not exist. Probably it's better to fill > them with zeros here. > Pre-memset was an optimization - it fills buffer only once instead on > each kpagecgroup_read() call. Ah, OK. So here's ver.2. Thanks, Naoya --- From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Subject: [PATCH v2] 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 <n-horiguchi@xxxxxxxxxxxxx> Suggested-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx> --- tools/vm/page-types.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) 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); -- 2.4.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>