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=-5.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 54295C4363A for ; Mon, 5 Oct 2020 06:05:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9FCAB207BC for ; Mon, 5 Oct 2020 06:05:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="AMSlD23D" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9FCAB207BC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C675B6B005D; Mon, 5 Oct 2020 02:05:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C18016B0062; Mon, 5 Oct 2020 02:05:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B06A68E0001; Mon, 5 Oct 2020 02:05:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0106.hostedemail.com [216.40.44.106]) by kanga.kvack.org (Postfix) with ESMTP id 81C666B005D for ; Mon, 5 Oct 2020 02:05:45 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 13730181AE874 for ; Mon, 5 Oct 2020 06:05:45 +0000 (UTC) X-FDA: 77336835450.26.mind25_2502aeb271bb Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id EAE8E1804B65A for ; Mon, 5 Oct 2020 06:05:44 +0000 (UTC) X-HE-Tag: mind25_2502aeb271bb X-Filterd-Recvd-Size: 3704 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Mon, 5 Oct 2020 06:05:44 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1601877943; 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: in-reply-to:in-reply-to:references:references; bh=H8PfrCBAkG4RHSNenftpNrKV45oZN++KpOv1lY8RxhI=; b=AMSlD23DVkzj83p2mRqdOShIUP2CnlG0OuXztm6X6sOhuignShWgnHp41MVLkRkUNA9JTi VFqh6BwQajMt+oH4+OV8IieUgyR6MWsaNrrdfS/nt4rKTqKZBN10RHMvPiYwr203frAZZA 2PALxEKSSGVm4wtsL15KHaot2kfgOqY= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 15145ABD1; Mon, 5 Oct 2020 06:05:43 +0000 (UTC) Date: Mon, 5 Oct 2020 08:05:42 +0200 From: Michal Hocko To: Anshuman Khandual Cc: linux-mm@kvack.org, Daniel Jordan , Zi Yan , John Hubbard , Mike Kravetz , Oscar Salvador , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [RFC V2] mm/vmstat: Add events for HugeTLB migration Message-ID: <20201005060542.GM4555@dhcp22.suse.cz> References: <1601445649-22163-1-git-send-email-anshuman.khandual@arm.com> <20201002120422.GE4555@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) 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 Mon 05-10-20 07:59:12, Anshuman Khandual wrote: > > > On 10/02/2020 05:34 PM, Michal Hocko wrote: > > On Wed 30-09-20 11:30:49, Anshuman Khandual wrote: > >> Add following new vmstat events which will track HugeTLB page migration. > >> > >> 1. HUGETLB_MIGRATION_SUCCESS > >> 2. HUGETLB_MIGRATION_FAILURE > >> > >> It follows the existing semantics to accommodate HugeTLB subpages in total > >> page migration statistics. While here, this updates current trace event > >> 'mm_migrate_pages' to accommodate now available HugeTLB based statistics. > > What is the actual usecase? And how do you deal with the complexity > > introduced by many different hugetlb page sizes. Really, what is the > > point to having such a detailed view on hugetlb migration? > > > > It helps differentiate various page migration events i.e normal, THP and > HugeTLB and gives us more reliable and accurate measurement. Current stats > as per PGMIGRATE_SUCCESS and PGMIGRATE_FAIL are misleading, as they contain > both normal and HugeTLB pages as single entities, which is not accurate. Yes this is true. But why does it really matter? Do you have a specific example? > After this change, PGMIGRATE_SUCCESS and PGMIGRATE_FAIL will contain page > migration statistics in terms of normal pages irrespective of whether any > previous migrations until that point involved normal pages, THP or HugeTLB > (any size) pages. At the least, this fixes existing misleading stats with > PGMIGRATE_SUCCESS and PGMIGRATE_FAIL. > > Besides, it helps us understand HugeTLB migrations in more detail. Even > though HugeTLB can be of various sizes on a given platform, these new > stats HUGETLB_MIGRATION_SUCCESS and HUGETLB_MIGRATION_FAILURE give enough > overall insight into HugeTLB migration events. While true this all is way too vague to add yet another imprecise counter. -- Michal Hocko SUSE Labs