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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 DF761C433E1 for ; Tue, 2 Jun 2020 04:21:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 956CA20738 for ; Tue, 2 Jun 2020 04:21:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 956CA20738 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 25E8680007; Tue, 2 Jun 2020 00:21:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 20F0A8E0006; Tue, 2 Jun 2020 00:21:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1247F80007; Tue, 2 Jun 2020 00:21:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0137.hostedemail.com [216.40.44.137]) by kanga.kvack.org (Postfix) with ESMTP id EEA658E0006 for ; Tue, 2 Jun 2020 00:21:35 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A5D8721F0 for ; Tue, 2 Jun 2020 04:21:35 +0000 (UTC) X-FDA: 76882972950.02.toys35_652ac79ae8f4f Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin02.hostedemail.com (Postfix) with ESMTP id 8F3374428 for ; Tue, 2 Jun 2020 04:21:35 +0000 (UTC) X-HE-Tag: toys35_652ac79ae8f4f X-Filterd-Recvd-Size: 3393 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Tue, 2 Jun 2020 04:21:35 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5BEC055D; Mon, 1 Jun 2020 21:21:34 -0700 (PDT) Received: from [192.168.0.129] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8C92D3F52E; Mon, 1 Jun 2020 21:21:31 -0700 (PDT) Subject: Re: [PATCH] mm/vmstat: Add events for PMD based THP migration without split To: John Hubbard , Daniel Jordan Cc: linux-mm@kvack.org, hughd@google.com, Naoya Horiguchi , Zi Yan , Andrew Morton , linux-kernel@vger.kernel.org References: <1590118444-21601-1-git-send-email-anshuman.khandual@arm.com> <20200601165736.qw5kwwknxltk7bv6@ca-dmjordan1.us.oracle.com> <0a936ec7-f44f-1d72-915f-f5758d25fd72@nvidia.com> From: Anshuman Khandual Message-ID: <1e71d815-5359-3ebe-5d2b-5a3b54b63b51@arm.com> Date: Tue, 2 Jun 2020 09:50:29 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <0a936ec7-f44f-1d72-915f-f5758d25fd72@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 8F3374428 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 06/02/2020 08:50 AM, John Hubbard wrote: > On 2020-06-01 09:57, Daniel Jordan wrote: >> Hi Anshuman, >> >> On Fri, May 22, 2020 at 09:04:04AM +0530, Anshuman Khandual wrote: >>> This adds the following two new VM events which will help in validating PMD >>> based THP migration without split. Statistics reported through these events >>> will help in performance debugging. >>> >>> 1. THP_PMD_MIGRATION_SUCCESS >>> 2. THP_PMD_MIGRATION_FAILURE >> >> The names suggest a binary event similar to the existing >> pgmigrate_success/fail, but FAILURE only tracks one kind of migration error, >> and then only when the thp is successfully split, so shouldn't it be called >> SPLIT instead? >> > > So the full description of the situation, which we're trying to compress into > a shorter name, is "THP pmd migration failure, due to successfully splitting > the THP". From that, the beginning part is the real point here, while the last > part is less important. In other words, the users of these events are people > who are trying to quantify THP migrations, and these events are particularly > relevant for that. The "THP migration failed" is more important here than > the reason that it failed. Or so I believe so far. Absolutely, these events really help in quantifying THP migration successes or their failures that involve splitting. > > So I still think that the names are really quite good, but your point is Agreed. > also important: maybe this patch should also be tracking other causes > of THP PMD migration failure, in order to get a truer accounting of the > situation. Is there any other failure reasons which are only specific to THP migration. Else, adding stats about generic migration failure reasons will just blur the overall understanding about THP migration successes and failure cases that results in splitting.