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[209.85.221.44]) by smtp.gmail.com with ESMTPSA id a1-20020a1709063e8100b006ce06ed8aa7sm7133435ejj.142.2022.04.20.13.07.42 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Apr 2022 13:07:42 -0700 (PDT) Received: by mail-wr1-f44.google.com with SMTP id u3so3762384wrg.3 for ; Wed, 20 Apr 2022 13:07:42 -0700 (PDT) X-Received: by 2002:ac2:4203:0:b0:448:8053:d402 with SMTP id y3-20020ac24203000000b004488053d402mr15354025lfh.687.1650485251826; Wed, 20 Apr 2022 13:07:31 -0700 (PDT) MIME-Version: 1.0 References: <20220407031525.2368067-1-yuzhao@google.com> <20220407031525.2368067-6-yuzhao@google.com> <20220411191615.a34959bdcc25ef3f9c16a7ce@linux-foundation.org> <20220412070616.GT2731@worktop.programming.kicks-ass.net> In-Reply-To: From: Linus Torvalds Date: Wed, 20 Apr 2022 13:07:15 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v10 05/14] mm: multi-gen LRU: groundwork To: Yu Zhao Cc: Peter Zijlstra , Andrew Morton , Stephen Rothwell , Linux-MM , Andi Kleen , Aneesh Kumar , Barry Song <21cnbao@gmail.com>, Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , Linux ARM , "open list:DOCUMENTATION" , linux-kernel , Kernel Page Reclaim v2 , "the arch/x86 maintainers" , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 19, 2022 at 5:39 PM Yu Zhao wrote: > > A related question: if I pass new = old to try_cmpxchg(), does it know > that and avoid an unnecessary atomic op? No. try_cmpxchg() basically translates directly to a cmpxchg instruction (on x86) with the return value being the eflags 'Z' bit. Linus 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6AD2FC433EF for ; Wed, 20 Apr 2022 20:09:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=alNvyKXqyEb/X+zjHBU1XWr5hFqk4hRgC5Z7SUPbOao=; b=xRkLr9QWyNS8Et 1BC4m1h1N3tUyDGH33EvpfuafuBpkGvGw7ZimLQ3baY3aYF6USDGOuyFsDQ1W3oV3E3u06JDAC6d9 iy90hT5yjnC0qwTiRZqMG+KbVdnaWsc3U4dhF0ykN6QWnUPpCjb4cE3Rf4hSoYN0uf+T/uLmDDFo3 ubwRLXY7bsB9FbYVg8KQWUqZgbcNwWREk/1g4y1m0teeeaUn2U1YkSDuWd64KcTIkQNQJTZNgzkQC hE0KjpTOawzAOI4T8AU7nNg6clojl/8uEteUezBVgq6fCveKBqp52qRSS9se2CEk6RIBnqoGXr8ED fILPWUUELoDMR1Ve9CdA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nhGcC-00AI00-HE; Wed, 20 Apr 2022 20:07:52 +0000 Received: from mail-ed1-x52c.google.com ([2a00:1450:4864:20::52c]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nhGc9-00AHwe-2U for linux-arm-kernel@lists.infradead.org; Wed, 20 Apr 2022 20:07:51 +0000 Received: by mail-ed1-x52c.google.com with SMTP id c64so3726520edf.11 for ; Wed, 20 Apr 2022 13:07:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=or6JCjKhYhBiaiW00aMF7rUmRM1Om7N8+nnkFL4bbB4=; b=PwJpWKVjNrMu7Gg4yVflFwYwWc4nnM7umtCY/l7yKXyV5Ft110X2v0svZpu5ToN4Y5 DixablUApzvMzWya52D6gsldNClKZ0hyWeT/vhefyz8p4NqsfRLxoQJka5SJ7qGYV5KB ffG4ldzo9WpYNDxAEPmlwy7ETPe2MogPwMbPI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=or6JCjKhYhBiaiW00aMF7rUmRM1Om7N8+nnkFL4bbB4=; b=KHnKrltaFZCN7LjTjMusAar4Orucdtq8FiT3u/qtQNtPdpJSJ17uvyuB/v/0/8eJux uyz++Z0szl1+qzCENpIL5a/zoBOAyOKR6APcDtv5CINUhmkDmM1gC06HoX30TdX1mlF1 mmcy8UJNCB2VCKBQYPvDaRcSXL+Pez20zX2YS2/z2hvcwogDbCLKT0hKdaXoqDsDp/I2 SlqlquB1DLHnncFmcv9abFQ04CQPecEclS8xWAuN/CsuR6cZ6FB2vo7eyUaTWFZQpMWn UXX/7h9+VcAJCHaT7KneK1uiAeAbLCGUtPrOR8127hLt4UNGCfNpNFEQ1TYLAYpQV4NM Tp4g== X-Gm-Message-State: AOAM530l+U3UYLDGLJRUpXtmbiJZlok/a0j29NGcxkftQHnIcyicw9ZZ iJuniZqOFvnnXQ3xfUDymWgiZsFN/x3Rr5GAn6Q= X-Google-Smtp-Source: ABdhPJwESbtxrnWHPjxUS1MrVHlaI4RE1LhCDsezU7WOIJmtgrx+H6PDpIkTFbS6+v0HN/y0s8WfFA== X-Received: by 2002:a05:6402:b57:b0:41d:6d9b:7e0d with SMTP id bx23-20020a0564020b5700b0041d6d9b7e0dmr25035593edb.78.1650485265022; Wed, 20 Apr 2022 13:07:45 -0700 (PDT) Received: from mail-ej1-f53.google.com (mail-ej1-f53.google.com. [209.85.218.53]) by smtp.gmail.com with ESMTPSA id l15-20020a170906938f00b006e8afb5a7d9sm6981423ejx.33.2022.04.20.13.07.42 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Apr 2022 13:07:42 -0700 (PDT) Received: by mail-ej1-f53.google.com with SMTP id y10so5741610ejw.8 for ; Wed, 20 Apr 2022 13:07:42 -0700 (PDT) X-Received: by 2002:ac2:4203:0:b0:448:8053:d402 with SMTP id y3-20020ac24203000000b004488053d402mr15354025lfh.687.1650485251826; Wed, 20 Apr 2022 13:07:31 -0700 (PDT) MIME-Version: 1.0 References: <20220407031525.2368067-1-yuzhao@google.com> <20220407031525.2368067-6-yuzhao@google.com> <20220411191615.a34959bdcc25ef3f9c16a7ce@linux-foundation.org> <20220412070616.GT2731@worktop.programming.kicks-ass.net> In-Reply-To: From: Linus Torvalds Date: Wed, 20 Apr 2022 13:07:15 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v10 05/14] mm: multi-gen LRU: groundwork To: Yu Zhao Cc: Peter Zijlstra , Andrew Morton , Stephen Rothwell , Linux-MM , Andi Kleen , Aneesh Kumar , Barry Song <21cnbao@gmail.com>, Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Michal Hocko , Mike Rapoport , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , Linux ARM , "open list:DOCUMENTATION" , linux-kernel , Kernel Page Reclaim v2 , "the arch/x86 maintainers" , Brian Geffon , Jan Alexander Steffens , Oleksandr Natalenko , Steven Barrett , Suleiman Souhlal , Daniel Byrne , Donald Carr , =?UTF-8?Q?Holger_Hoffst=C3=A4tte?= , Konstantin Kharlamov , Shuang Zhai , Sofia Trinh , Vaibhav Jain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220420_130749_143033_C66236F7 X-CRM114-Status: GOOD ( 11.08 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Apr 19, 2022 at 5:39 PM Yu Zhao wrote: > > A related question: if I pass new = old to try_cmpxchg(), does it know > that and avoid an unnecessary atomic op? No. try_cmpxchg() basically translates directly to a cmpxchg instruction (on x86) with the return value being the eflags 'Z' bit. Linus _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel