From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752592AbbAIBEd (ORCPT ); Thu, 8 Jan 2015 20:04:33 -0500 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:35681 "EHLO lgemrelse6q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750949AbbAIBEc (ORCPT ); Thu, 8 Jan 2015 20:04:32 -0500 X-Original-SENDERIP: 10.177.222.153 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Fri, 9 Jan 2015 10:04:42 +0900 From: Joonsoo Kim To: Vlastimil Babka Cc: Andrew Morton , Mel Gorman , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] mm/compaction: enhance trace output to know more about compaction internals Message-ID: <20150109010441.GA27760@js1304-P5Q-DELUXE> References: <1417593127-6819-1-git-send-email-iamjoonsoo.kim@lge.com> <54ABA563.1040103@suse.cz> <20150108081835.GC25453@js1304-P5Q-DELUXE> <54AE43E3.60209@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54AE43E3.60209@suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 08, 2015 at 09:46:27AM +0100, Vlastimil Babka wrote: > 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. Okay. > > >> 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. Ah... now I see your point and found my mistake. My intention is also to print terminated pfn rather than end_pfn of pageblock. :/ I will change it to print pfn where we terminate scanning. Thanks.