From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f47.google.com (mail-pa0-f47.google.com [209.85.220.47]) by kanga.kvack.org (Postfix) with ESMTP id 751F36B0036 for ; Mon, 4 Nov 2013 02:05:06 -0500 (EST) Received: by mail-pa0-f47.google.com with SMTP id lf10so6568825pab.34 for ; Sun, 03 Nov 2013 23:05:06 -0800 (PST) Received: from psmtp.com ([74.125.245.113]) by mx.google.com with SMTP id it5si9740747pbc.95.2013.11.03.23.05.04 for ; Sun, 03 Nov 2013 23:05:05 -0800 (PST) Received: by mail-ee0-f54.google.com with SMTP id c50so905117eek.27 for ; Sun, 03 Nov 2013 23:05:02 -0800 (PST) Date: Mon, 4 Nov 2013 08:05:00 +0100 From: Ingo Molnar Subject: Re: [PATCH] mm: cache largest vma Message-ID: <20131104070500.GE13030@gmail.com> References: <1383337039.2653.18.camel@buesod1.americas.hpqcorp.net> <20131103101234.GB5330@gmail.com> <1383538810.2373.22.camel@buesod1.americas.hpqcorp.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1383538810.2373.22.camel@buesod1.americas.hpqcorp.net> Sender: owner-linux-mm@kvack.org List-ID: To: Davidlohr Bueso , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker Cc: Andrew Morton , Hugh Dickins , Michel Lespinasse , Mel Gorman , Rik van Riel , Guan Xuetao , aswin@hp.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds * Davidlohr Bueso wrote: > Btw, do you suggest using a high level tool such as perf for getting > this data or sprinkling get_cycles() in find_vma() -- I'd think that the > first isn't fine grained enough, while the later will probably variate a > lot from run to run but the ratio should be rather constant. LOL - I guess I should have read your mail before replying to it ;-) Yes, I think get_cycles() works better in this case - not due to granularity (perf stat will report cycle granular just fine), but due to the size of the critical path you'll be measuring. You really want to extract the delta, because it's probably so much smaller than the overhead of the workload itself. [ We still don't have good 'measure overhead from instruction X to instruction Y' delta measurement infrastructure in perf yet, although Frederic is working on such a trigger/delta facility AFAIK. ] Thanks, Ingo -- 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