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=-6.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS 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 8B73AC2B9F4 for ; Tue, 15 Jun 2021 02:04:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0F39161421 for ; Tue, 15 Jun 2021 02:04:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0F39161421 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 60AE66B0036; Mon, 14 Jun 2021 22:04:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5BB2C6B006E; Mon, 14 Jun 2021 22:04:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 45BDA6B0070; Mon, 14 Jun 2021 22:04:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0105.hostedemail.com [216.40.44.105]) by kanga.kvack.org (Postfix) with ESMTP id 0F95F6B0036 for ; Mon, 14 Jun 2021 22:04:23 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 9305E8249980 for ; Tue, 15 Jun 2021 02:04:22 +0000 (UTC) X-FDA: 78254313564.12.A5A9ED0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf13.hostedemail.com (Postfix) with ESMTP id A3F5AE000251 for ; Tue, 15 Jun 2021 02:04:13 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id E10946141D; Tue, 15 Jun 2021 02:04:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1623722661; bh=fy4A+rMup3zzCXF8eOlXYREttBkOQdv3a/7hhAjw8vc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=EdZaWbEDw2wM2ePbIhPOZIefDrmg9M16+h81cAU4GOfejqvI3SowrKRcUT/SzeRT5 oZ8426A+qh+XG5uYv/CAJRdi/h+aM3WP6rro8EyIvlTsO/TBMBF05/IkR8wKnTuTFO ThsIuG53MrYZt6lZL+MM0tcQzkVacsz7mLBX8pdE= Date: Mon, 14 Jun 2021 19:04:20 -0700 From: Andrew Morton To: SeongJae Park Cc: "Matthew Wilcox (Oracle)" , akpm@linuxfoundation.org, linux-mm@kvack.org, Heiko Carstens , Rafael Aquini , Vlastimil Babka , Yu Zhao , Vladimir Davydov , kirill.shutemov@linux.intel.com, amit@kernel.org Subject: Re: [PATCH] mm: Mark idle page tracking as BROKEN Message-Id: <20210614190420.af6bb3ca193541cdb606517d@linux-foundation.org> In-Reply-To: <20210614134926.17279-1-sjpark@amazon.de> References: <20210612000714.775825-1-willy@infradead.org> <20210614134926.17279-1-sjpark@amazon.de> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: A3F5AE000251 Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=EdZaWbED; spf=pass (imf13.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Stat-Signature: gse4ha7fonuh6hfbt8dn73cucf8saiyc X-HE-Tag: 1623722653-527279 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, 14 Jun 2021 13:49:26 +0000 SeongJae Park wrote: > From: SeongJae Park > > Hello Matthew, > > On Sat, 12 Jun 2021 01:07:14 +0100 "Matthew Wilcox (Oracle)" wrote: > > > In discussion with other MM developers around how idle page tracking > > should be fixed for transparent huge pages, several expressed the opinion > > that it should be removed as it is inefficient at accomplishing the > > job that it is supposed to, and we have better mechanisms (eg uffd) for > > accomplishing the same goals these days. > > I think the THP case[1] is an intended behavior[2]. Could you please share a > link to the discussion or a detailed summary if possible? > > > > > Mark the feature as BROKEN for now and we can remove it entirely in a > > few months if nobody complains. It is not enabled by Android, ChromeOS, > > Debian, Fedora or SUSE. Red Hat enabled it with RHEL-8.1 and UEK followed > > suit, but I have been unable to find why RHEL enabled it. > > Amazon Linux is also using it[3], for DAMON[4]. In detail, DAMON doesn't use > Idle Page Tracking but PG_Idle in kernel space, to avoid interfering the > reclaim logic[5]. So, I'm ok with removing the Idle Page Tracking user space > interface, but gonna be opposed to removing PG_Idle. > > Nevertheless, the interference is not a real problem to DAMON, as DAMON is > aimed to provide just a reasonable quality of the monitoring, rather than > strict correctness. Hence, if people think the interference is also not a > problem for the reclaim logic (after all, it does nothing unless sysadmin > manually turns it on in runtime, and can be turned off at anytime), I would > simply update DAMON code to don't use PG_Idle, add warnings in the doc, and > wouldn't be opposed to this change. Couldn't the DAMON patchset simply re-add PG_Idle? Perhaps with a new name which is more appropriate to the DAMON usage?