From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757897AbcG0Sot (ORCPT ); Wed, 27 Jul 2016 14:44:49 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:34413 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756845AbcG0Sos (ORCPT ); Wed, 27 Jul 2016 14:44:48 -0400 Date: Wed, 27 Jul 2016 20:44:45 +0200 From: Michal Hocko To: Rik van Riel Cc: Janani Ravichandran , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, hannes@compxchg.org, vdavydov@virtuozzo.com, vbabka@suse.cz, mgorman@techsingularity.net, kirill.shutemov@linux.intel.com, bywxiaobai@163.com, rostedt@goodmis.org Subject: Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath Message-ID: <20160727184445.GG21859@dhcp22.suse.cz> References: <6b12aed89ad75cb2b3525a24265fa1d622409b42.1469629027.git.janani.rvchndrn@gmail.com> <20160727163351.GC21859@dhcp22.suse.cz> <1469643382.10218.20.camel@surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1469643382.10218.20.camel@surriel.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 27-07-16 14:16:22, Rik van Riel wrote: > On Wed, 2016-07-27 at 18:33 +0200, Michal Hocko wrote: > > On Wed 27-07-16 10:47:59, Janani Ravichandran wrote: > > > > > > Add tracepoints to the slowpath code to gather some information. > > > The tracepoints can also be used to find out how much time was > > > spent in > > > the slowpath. > > I do not think this is a right thing to measure. > > __alloc_pages_slowpath > > is more a code organization thing. The fast path might perform an > > expensive operations like zone reclaim (if node_reclaim_mode > 0) so > > these trace point would miss it. > > It doesn't look like it does. The fast path either > returns an allocated page to the caller, or calls > into the slow path. I must be missing something here but what prevents __alloc_pages_nodemask->get_page_from_freelist from doing zone_reclaim? -- Michal Hocko SUSE Labs