Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753908AbcCHFMS (ORCPT ); Tue, 8 Mar 2016 00:12:18 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:34700 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750891AbcCHFML (ORCPT ); Tue, 8 Mar 2016 00:12:11 -0500 MIME-Version: 1.0 In-Reply-To: <1457401652-9226-1-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1457401652-9226-1-git-send-email-n-horiguchi@ah.jp.nec.com> Date: Tue, 8 Mar 2016 08:12:09 +0300 Message-ID: Subject: Re: [PATCH v1] tools/vm/page-types.c: remove memset() in walk_pfn() From: Konstantin Khlebnikov To: Naoya Horiguchi Cc: "linux-mm@kvack.org" , Andrew Morton , Vladimir Davydov , Linux Kernel Mailing List , Naoya Horiguchi Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2028 Lines: 62 On Tue, Mar 8, 2016 at 4:47 AM, Naoya Horiguchi 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. You could add fast-path for count=1 @@ -633,7 +633,10 @@ static void walk_pfn(unsigned long voffset, unsigned long pages; unsigned long i; - memset(cgi, 0, sizeof cgi); + if (count == 1) + cgi[0] = 0; + else + memset(cgi, 0, sizeof cgi); while (count) { batch = min_t(unsigned long, count, KPAGEFLAGS_BATCH); > > Fixes: 954e95584579 ("tools/vm/page-types.c: add memory cgroup dumping and filtering") > Signed-off-by: Naoya Horiguchi > --- > tools/vm/page-types.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git v4.5-rc5-mmotm-2016-02-24-16-18/tools/vm/page-types.c v4.5-rc5-mmotm-2016-02-24-16-18_patched/tools/vm/page-types.c > index dab61c3..c192baf 100644 > --- v4.5-rc5-mmotm-2016-02-24-16-18/tools/vm/page-types.c > +++ v4.5-rc5-mmotm-2016-02-24-16-18_patched/tools/vm/page-types.c > @@ -633,8 +633,6 @@ static void walk_pfn(unsigned long voffset, > unsigned long pages; > unsigned long i; > > - memset(cgi, 0, sizeof cgi); > - > while (count) { > batch = min_t(unsigned long, count, KPAGEFLAGS_BATCH); > pages = kpageflags_read(buf, index, batch); > -- > 2.7.0 >