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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 611BFC4332F for ; Thu, 3 Feb 2022 18:53:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C172D6B0071; Thu, 3 Feb 2022 13:53:55 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BC5A36B0072; Thu, 3 Feb 2022 13:53:55 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A8D916B0074; Thu, 3 Feb 2022 13:53:55 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0222.hostedemail.com [216.40.44.222]) by kanga.kvack.org (Postfix) with ESMTP id 95E216B0071 for ; Thu, 3 Feb 2022 13:53:55 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 55A8B95C82 for ; Thu, 3 Feb 2022 18:53:55 +0000 (UTC) X-FDA: 79102368030.07.CD660A3 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf17.hostedemail.com (Postfix) with ESMTP id 0816540003 for ; Thu, 3 Feb 2022 18:53:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643914434; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=X9DO1jLJUL5DivNcmSp8xo0wxBcJI5YNywWCMphqcSI=; b=BJphYcnGzBKbBWUfk1Ge+NIepU8XwySjPV82wyQ3nWpwATOJpBs5jRgy3+gYKGl0IDqKld DnVYjCQROUuur6MTDlFKr3z2dCHc3uUEBR6ik6En2W3Q6OOnjK3aw4xjV4Zsuxl8g37RNn OsrzSzTjYcONv3o/u6i4KqOfEyJmmFc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-594-J2BTooLXNPSbyWiBLp1SPA-1; Thu, 03 Feb 2022 13:53:49 -0500 X-MC-Unique: J2BTooLXNPSbyWiBLp1SPA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0D0AD81432F; Thu, 3 Feb 2022 18:53:46 +0000 (UTC) Received: from [10.22.8.80] (unknown [10.22.8.80]) by smtp.corp.redhat.com (Postfix) with ESMTP id CF03B7EFDD; Thu, 3 Feb 2022 18:53:10 +0000 (UTC) Message-ID: <88619dad-6d41-6a91-a8d6-72e3aaf3575d@redhat.com> Date: Thu, 3 Feb 2022 13:53:10 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH v4 4/4] mm/page_owner: Record task command name Content-Language: en-US To: Vlastimil Babka , Michal Hocko Cc: Johannes Weiner , Vladimir Davydov , Andrew Morton , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Ira Weiny , Mike Rapoport , David Rientjes , Roman Gushchin , Rafael Aquini References: <20220131192308.608837-5-longman@redhat.com> <20220131220328.622162-1-longman@redhat.com> <4ba66abe-5c6d-26a7-f11c-c3b8514bfb34@redhat.com> <91fb8637-6550-dc37-a95b-df7812b02b0a@suse.cz> From: Waiman Long In-Reply-To: <91fb8637-6550-dc37-a95b-df7812b02b0a@suse.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Stat-Signature: pt6foszn9yxbyoxh7ai1144ex5b8h68t X-Rspam-User: nil Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=BJphYcnG; spf=none (imf17.hostedemail.com: domain of longman@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 0816540003 X-HE-Tag: 1643914434-321 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2/3/22 07:10, Vlastimil Babka wrote: > On 2/2/22 17:53, Waiman Long wrote: >> On 2/1/22 10:28, Michal Hocko wrote: >>> Cc Vlastimil >>> >>> On Mon 31-01-22 17:03:28, Waiman Long wrote: >>>> The page_owner information currently includes the pid of the calling >>>> task. That is useful as long as the task is still running. Otherwise, >>>> the number is meaningless. To have more information about the allocating >>>> tasks that had exited by the time the page_owner information is >>>> retrieved, we need to store the command name of the task. >>>> >>>> Add a new comm field into page_owner structure to store the command name >>>> and display it when the page_owner information is retrieved. >>> I completely agree that pid is effectivelly useless (if not misleading) >>> but is comm really telling all that much to compensate for the >>> additional storage required for _each_ page in the system? >> Yes, it does add an extra 16 bytes per page overhead. The command name can >> be useful if one want to find out which userspace command is responsible for >> a problematic page allocation. Maybe we can remove pid from page_owner to >> save 8 bytes as you also agree that this number is not that useful. > Pid could be used to correlate command instances (not perfectly if reuse > happens), but command name could have a higher chance to be useful. In my > experience the most useful were the stacktraces and gfp/order etc. anyway. > So I wouldn't be opposed replacing pid with comm. The mild size increase > should be acceptable, this is an opt-in feature for debugging sessions with > known tradeoff for memory and cpu overhead for the extra info. Thanks for the information. I floated around dropping pid just as a possible way to reduce overall memory overhead. I did not do that in my patch and I am not planning to post any patch unless everybody agree. Cheer, Longman