From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 1E6706B0033 for ; Thu, 23 Nov 2017 09:01:30 -0500 (EST) Received: by mail-wm0-f69.google.com with SMTP id n8so4981574wmg.4 for ; Thu, 23 Nov 2017 06:01:30 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id x9si9401353edh.429.2017.11.23.06.01.28 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 23 Nov 2017 06:01:28 -0800 (PST) Date: Thu, 23 Nov 2017 15:01:27 +0100 From: Michal Hocko Subject: Re: [PATCH] Add slowpath enter/exit trace events Message-ID: <20171123140127.7z5z6awj2ti6lozh@dhcp22.suse.cz> References: <20171123104336.25855-1-peter.enderborg@sony.com> <20171123122530.ktsxgeakebfp3yep@dhcp22.suse.cz> <20171123133629.5sgmapfg7gix7pu3@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171123133629.5sgmapfg7gix7pu3@techsingularity.net> Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: peter.enderborg@sony.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Steven Rostedt , Ingo Molnar , Alex Deucher , "David S . Miller" , Harry Wentland , Greg Kroah-Hartman , Tony Cheng , Andrew Morton , Vlastimil Babka , Johannes Weiner , Pavel Tatashin On Thu 23-11-17 13:36:29, Mel Gorman wrote: > On Thu, Nov 23, 2017 at 01:25:30PM +0100, Michal Hocko wrote: > > On Thu 23-11-17 11:43:36, peter.enderborg@sony.com wrote: > > > From: Peter Enderborg > > > > > > The warning of slow allocation has been removed, this is > > > a other way to fetch that information. But you need > > > to enable the trace. The exit function also returns > > > information about the number of retries, how long > > > it was stalled and failure reason if that happened. > > > > I think this is just too excessive. We already have a tracepoint for the > > allocation exit. All we need is an entry to have a base to compare with. > > Another usecase would be to measure allocation latency. Information you > > are adding can be (partially) covered by existing tracepoints. > > > > You can gather that by simply adding a probe to __alloc_pages_slowpath > (like what perf probe does) and matching the trigger with the existing > mm_page_alloc points. I am not sure adding a probe on a production system will fly in many cases. A static tracepoint would be much easier in that case. But I agree there are other means to accomplish the same thing. My main point was to have an easy out-of-the-box way to check latencies. But that is not something I would really insist on. -- Michal Hocko SUSE Labs -- 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