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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 42423C433E0 for ; Thu, 7 Jan 2021 02:53:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9B29522E03 for ; Thu, 7 Jan 2021 02:53:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9B29522E03 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bytedance.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CED828D0115; Wed, 6 Jan 2021 21:53:03 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C76D68D0090; Wed, 6 Jan 2021 21:53:03 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B8A638D0115; Wed, 6 Jan 2021 21:53:03 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0065.hostedemail.com [216.40.44.65]) by kanga.kvack.org (Postfix) with ESMTP id A173D8D0090 for ; Wed, 6 Jan 2021 21:53:03 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 643C3824556B for ; Thu, 7 Jan 2021 02:53:03 +0000 (UTC) X-FDA: 77677457046.02.arm28_290e160274e6 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin02.hostedemail.com (Postfix) with ESMTP id 3D99810097AA0 for ; Thu, 7 Jan 2021 02:53:03 +0000 (UTC) X-HE-Tag: arm28_290e160274e6 X-Filterd-Recvd-Size: 3457 Received: from mail-pf1-f177.google.com (mail-pf1-f177.google.com [209.85.210.177]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Thu, 7 Jan 2021 02:53:02 +0000 (UTC) Received: by mail-pf1-f177.google.com with SMTP id s21so2931613pfu.13 for ; Wed, 06 Jan 2021 18:53:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=xjM/12FZ440jYsJkVJrWv4LsYWfcjGwNNBn9yloYJhQ=; b=AmbNg67TWQuuAe08RuN+7R2vJB69lMLJRGhpJ/K1pSCxw8TJUTOQQYXadvlMBZ2EpW DwzK57DTuLMA7YvnQ+aHMi0/YIhtDU+9FDz/1p4qlqtaBzF30xazKzFdzE5ObatvUIa3 YHADcrUF+7BCL4QGvaXltlXz71cJ1n1GXSqxHbnJZq0R5ZP+VIoMKIIkgyfsg96RoBs4 rvA6CbrTYLFl8yyy/K1GJ/iIPF6xgfEfcPpHStj8iMZvYLGcon1nE31CUQiGSFPeDI+W D09cpTTipC1sT6OJ6eNNUKeeHw61rUmuj6Mkv/+IMMQvasYBTqBm32CCKzq14Bsjf9Ri VgJA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=xjM/12FZ440jYsJkVJrWv4LsYWfcjGwNNBn9yloYJhQ=; b=ZO4V9c4tajjgaCyr6LKC4TRJQHXfIlRtewlZ5kYWm1a/8Y1NlprMCcaVAYbsPLVWyp RH3TYN2QVn/jiUByCjnpjXRc6GSLPX7c8SIN/hQy1NkRm8jl3OHy3fuD02CqLaDGfMQy Sgb5qsKYKWnYHIvXJ/GKhhabiztwRRNqqpGrgxd4LPnIxxQgRXCYq5OXVsORwwfI7LCl wH8iW40o0UhHc0XkGBjWRPLeQW8LAulez6Jk+qmP7Qwst4/3Ix3+HYKiksECyDsATKXe zElUKSDW7rl7RQm3p9ch5+ufcpCiyDmR8akmBsDWQ6BYArd/6Ftvi7aelcDLc5qTrs3T vlqA== X-Gm-Message-State: AOAM531da8tqcSPcKNExSA6GNjVlwJ5LOC6Sj0zwkIUu+91QoU9kfDHh OFRUyTJOFPMbDuIjzResKsBH8+/LVJbGBbi92UAbcQ== X-Google-Smtp-Source: ABdhPJwQ6lLwtKUmB5u0bfXMnFW/1FXwZEG1smcYuzInOoacCoij6J4Pd4ZSgfvOX2D82Fr+7TSTGXafXy2ks+cOigw= X-Received: by 2002:aa7:979d:0:b029:1a4:3b76:a559 with SMTP id o29-20020aa7979d0000b02901a43b76a559mr6601863pfp.49.1609987979866; Wed, 06 Jan 2021 18:52:59 -0800 (PST) MIME-Version: 1.0 References: <20210106084739.63318-1-songmuchun@bytedance.com> <20210106084739.63318-2-songmuchun@bytedance.com> <20210106161327.GR13207@dhcp22.suse.cz> In-Reply-To: <20210106161327.GR13207@dhcp22.suse.cz> From: Muchun Song Date: Thu, 7 Jan 2021 10:52:21 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v2 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one To: Michal Hocko Cc: Mike Kravetz , Andrew Morton , Naoya Horiguchi , Andi Kleen , Linux Memory Management List , LKML , Yang Shi Content-Type: text/plain; charset="UTF-8" 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 Thu, Jan 7, 2021 at 12:13 AM Michal Hocko wrote: > > On Wed 06-01-21 16:47:34, Muchun Song wrote: > > If the refcount is one when it is migrated, it means that the page > > was freed from under us. So we are done and do not need to migrate. > > Is this common enough that it would warrant the explicit check for each > migration? Are you worried about the overhead caused by the check? Thanks. > -- > Michal Hocko > SUSE Labs