From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 76EB36B0253 for ; Wed, 27 Jul 2016 13:20:50 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id w128so3914632pfd.3 for ; Wed, 27 Jul 2016 10:20:50 -0700 (PDT) Received: from mga09.intel.com (mga09.intel.com. [134.134.136.24]) by mx.google.com with ESMTP id m6si7333138pfj.88.2016.07.27.10.20.49 for ; Wed, 27 Jul 2016 10:20:49 -0700 (PDT) Subject: Re: [PATCH 1/2] mm: page_alloc.c: Add tracepoints for slowpath References: <6b12aed89ad75cb2b3525a24265fa1d622409b42.1469629027.git.janani.rvchndrn@gmail.com> <20160727112303.11409a4e@gandalf.local.home> From: Dave Hansen Message-ID: <5798ED5C.1020300@intel.com> Date: Wed, 27 Jul 2016 10:20:28 -0700 MIME-Version: 1.0 In-Reply-To: <20160727112303.11409a4e@gandalf.local.home> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Steven Rostedt , Janani Ravichandran Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, riel@surriel.com, akpm@linux-foundation.org, hannes@compxchg.org, vdavydov@virtuozzo.com, mhocko@suse.com, vbabka@suse.cz, mgorman@techsingularity.net, kirill.shutemov@linux.intel.com, bywxiaobai@163.com On 07/27/2016 08:23 AM, Steven Rostedt wrote: >> > + >> > + trace_mm_slowpath_end(page); >> > + > I'm thinking you only need one tracepoint, and use function_graph > tracer for the length of the function call. > > # cd /sys/kernel/debug/tracing > # echo __alloc_pages_nodemask > set_ftrace_filter > # echo function_graph > current_tracer > # echo 1 > events/kmem/trace_mm_slowpath/enable I hesitate to endorse using the function_graph tracer for this kind of stuff. Tracepoints offer some level of stability in naming, and the compiler won't ever make them go away. While __alloc_pages_nodemask is probably more stable than most things, there's no guarantee that it will be there. BTW, what's the overhead of the function graph tracer if the filter is set up to be really restrictive like above? Is the overhead really just limited to that one function? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org