From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f179.google.com (mail-wi0-f179.google.com [209.85.212.179]) by kanga.kvack.org (Postfix) with ESMTP id BC8C46B0073 for ; Thu, 8 Jan 2015 03:46:30 -0500 (EST) Received: by mail-wi0-f179.google.com with SMTP id ex7so1743919wid.0 for ; Thu, 08 Jan 2015 00:46:30 -0800 (PST) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id hz2si10467329wjb.173.2015.01.08.00.46.29 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 08 Jan 2015 00:46:29 -0800 (PST) Message-ID: <54AE43E3.60209@suse.cz> Date: Thu, 08 Jan 2015 09:46:27 +0100 From: Vlastimil Babka MIME-Version: 1.0 Subject: Re: [PATCH 1/3] mm/compaction: enhance trace output to know more about compaction internals References: <1417593127-6819-1-git-send-email-iamjoonsoo.kim@lge.com> <54ABA563.1040103@suse.cz> <20150108081835.GC25453@js1304-P5Q-DELUXE> In-Reply-To: <20150108081835.GC25453@js1304-P5Q-DELUXE> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Andrew Morton , Mel Gorman , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 01/08/2015 09:18 AM, Joonsoo Kim wrote: > On Tue, Jan 06, 2015 at 10:05:39AM +0100, Vlastimil Babka wrote: >> On 12/03/2014 08:52 AM, Joonsoo Kim wrote: >> > It'd be useful to know where the both scanner is start. And, it also be >> > useful to know current range where compaction work. It will help to find >> > odd behaviour or problem on compaction. >> >> Overall it looks good, just two questions: >> 1) Why change the pfn output to hexadecimal with different printf layout and >> change the variable names and? Is it that better to warrant people having to >> potentially modify their scripts parsing the old output? > > Deciaml output has really bad readability since we manage all pages by order > of 2 which is well represented by hexadecimal. With hex output, we can > easily notice whether we move out from one pageblock to another one. OK. I don't have any strong objection, maybe Mel should comment on this as the author of most of the tracepoints? But if it happens, I think converting the old tracepoints to new hexadecimal format should be a separate patch from adding the new ones. >> 2) Would it be useful to also print in the mm_compaction_isolate_template based >> tracepoints, pfn of where the particular scanner left off a block prematurely? >> It doesn't always match start_pfn + nr_scanned. > > With start_pfn and end_pfn, detailed analysis is possible. We can know pageblock > where we actually scan and isolate and how much pages we try in that > pageblock and can guess why it doesn't become freepage with pageblock > order roughly. > > nr_scanned is just different metric. end_pfn don't need to match with > start_pfn + nr_scanned. Well that's part of my point. end_pfn is the end of the pageblock. nr_scanned might be lower than end_pfn - start_pfn, because we terminate in the middle of the pageblock. But it might be also lower, because we e.g. skip higher-order free pages. So we don't recognize where we terminated early. > Thanks. > > -- > 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 > -- 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