From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D5001C3E8C5 for ; Fri, 27 Nov 2020 19:10:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 78B11221F1 for ; Fri, 27 Nov 2020 19:10:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730320AbgK0TJv (ORCPT ); Fri, 27 Nov 2020 14:09:51 -0500 Received: from mx2.suse.de ([195.135.220.15]:48502 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730167AbgK0THG (ORCPT ); Fri, 27 Nov 2020 14:07:06 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7D4F5AC0C; Fri, 27 Nov 2020 19:06:38 +0000 (UTC) Subject: Re: [PATCH] mm/page_owner: Record timestamp and pid To: Georgi Djakov , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, sudaraja@codeaurora.org, pratikp@codeaurora.org, lmark@codeaurora.org References: <20201112184106.733-1-georgi.djakov@linaro.org> <20201112111436.c5deeadd3578877fc0b844a1@linux-foundation.org> <02f682e2-0e9b-76a8-04fa-487891e18bdf@suse.cz> <3ef3d770-d74b-5588-6672-f092c1526461@linaro.org> From: Vlastimil Babka Message-ID: Date: Fri, 27 Nov 2020 20:06:38 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <3ef3d770-d74b-5588-6672-f092c1526461@linaro.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/27/20 7:57 PM, Georgi Djakov wrote: > Hi Vlastimil, > > Thanks for the comment! > > On 11/27/20 19:52, Vlastimil Babka wrote: >> On 11/12/20 8:14 PM, Andrew Morton wrote: >>> On Thu, 12 Nov 2020 20:41:06 +0200 Georgi Djakov >>> wrote: >>> >>>> From: Liam Mark >>>> >>>> Collect the time for each allocation recorded in page owner so that >>>> allocation "surges" can be measured. >>>> >>>> Record the pid for each allocation recorded in page owner so that >>>> the source of allocation "surges" can be better identified. >>> >>> Please provide a description of why this is considered useful.  What >>> has it been used for, what problems has it been used to solve? >> >> Worth noting that on x86_64 it doubles the size of struct page_owner >> from 16 bytes to 32, so it better be justified: > > Well, that's true. But for debug options there is almost always some penalty. > The timestamp and pid information is very useful for me (and others, i believe) > when doing memory analysis. On a crash for example, we can get this information > from kdump (or RAM-dump) and look into it to catch memory allocation problems > more easily. Right. Btw, you should add printing the info to __dump_page_owner(). > If you find the above argument not strong enough, how about a separate config > option for this? Maybe something like CONFIG_PAGE_OWNER_EXTENDED, which could > be enabled in addition to CONFIG_PAGE_OWNER? It might be strong enough if it's mentioned in changelog, and also what exactly the space tradeoff is :) You can also mention that SLUB object tracking has also pid+timestamp. > Thanks, > Georgi > >> >> struct page_owner { >>         short unsigned int         order;                /*     0     2 */ >>         short int                  last_migrate_reason;  /*     2     2 */ >>         gfp_t                      gfp_mask;             /*     4     4 */ >>         depot_stack_handle_t       handle;               /*     8     4 */ >>         depot_stack_handle_t       free_handle;          /*    12     4 */ >>         u64                        ts_nsec;              /*    16     8 */ >>         int                        pid;                  /*    24     4 */ >> >>         /* size: 32, cachelines: 1, members: 7 */ >>         /* padding: 4 */ >>         /* last cacheline: 32 bytes */ >> }; >> >