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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 9820EC433DB for ; Wed, 17 Feb 2021 21:17:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4AE1564E58 for ; Wed, 17 Feb 2021 21:17:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4AE1564E58 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D80A56B0006; Wed, 17 Feb 2021 16:17:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D2FE56B006C; Wed, 17 Feb 2021 16:17:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C472D6B006E; Wed, 17 Feb 2021 16:17:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0068.hostedemail.com [216.40.44.68]) by kanga.kvack.org (Postfix) with ESMTP id AFC2B6B0006 for ; Wed, 17 Feb 2021 16:17:12 -0500 (EST) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 67E03BF1A for ; Wed, 17 Feb 2021 21:17:12 +0000 (UTC) X-FDA: 77829020304.14.wound71_0d052be2764f Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id 4B6F51808317E for ; Wed, 17 Feb 2021 21:17:12 +0000 (UTC) X-HE-Tag: wound71_0d052be2764f X-Filterd-Recvd-Size: 2434 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Wed, 17 Feb 2021 21:17:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=SNT38Fllc6tHutd44Y7GFooJxf2Yr4uXKo6Dx/78xZs=; b=ko737ihvincKwgVwE+SBcA7l+I XWxZegvieOZAgBBTlEL9fgJpmPxLWd1jW5LPbEkvD+IQrCs6O/lXQLANBJlRnEJ/saZx+xpqW7i9X dz3M4lraunZrtQQLvjWziGj9RFZ1zW1xH25nFhdHYJoLXp3z8Iz1avEaQ6061bJEATQ782M0ZlRuy e5JSMA5V2eNJM+r2xXLF1wddHA5hUEc53DRVkWyF88OvTMOzp9vno14qfS4/M5YEAnUyVGLyIfqJ3 jpsfb8ybZEPocMAlbcSGeVhLvbSslSWnImecTtH0vqIzsVDzKEWd7VjB6W9MaWvc2Y90ulCKYDIUO dAs0ovjQ==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lCUBA-000tCV-NY; Wed, 17 Feb 2021 21:16:28 +0000 Date: Wed, 17 Feb 2021 21:16:12 +0000 From: Matthew Wilcox To: Minchan Kim Cc: Michal Hocko , Andrew Morton , linux-mm , LKML , cgoldswo@codeaurora.org, linux-fsdevel@vger.kernel.org, david@redhat.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, joaodias@google.com Subject: Re: [RFC 1/2] mm: disable LRU pagevec during the migration temporarily Message-ID: <20210217211612.GO2858050@casper.infradead.org> References: <20210216170348.1513483-1-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Wed, Feb 17, 2021 at 12:46:19PM -0800, Minchan Kim wrote: > > I suspect you do not want to add atomic_read inside hot paths, right? Is > > this really something that we have to microoptimize for? atomic_read is > > a simple READ_ONCE on many archs. > > It's also spin_lock_irq_save in some arch. If the new synchonization is > heavily compilcated, atomic would be better for simple start but I thought > this locking scheme is too simple so no need to add atomic operation in > readside. What arch uses a spinlock for atomic_read()? I just had a quick grep and didn't see any.