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,URIBL_BLOCKED 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 B7F7CC433E6 for ; Thu, 7 Jan 2021 02:53:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 679B122E03 for ; Thu, 7 Jan 2021 02:53:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726658AbhAGCxl (ORCPT ); Wed, 6 Jan 2021 21:53:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725789AbhAGCxk (ORCPT ); Wed, 6 Jan 2021 21:53:40 -0500 Received: from mail-pg1-x52d.google.com (mail-pg1-x52d.google.com [IPv6:2607:f8b0:4864:20::52d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84042C0612EF for ; Wed, 6 Jan 2021 18:53:00 -0800 (PST) Received: by mail-pg1-x52d.google.com with SMTP id g15so3792346pgu.9 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=CJGEUe9Qle1PBSSb9K+fytc915YcO69NAkp55BSCU9BhoPF+DTkmm7b9vRo5IVz+4r 7h0vsouboyB5zENq6o3WG0GntueEbx18c/LVrI8neQqkwktGpLTJnb4EdfR3f7Vn645s kIoV8+6oDsdybwybFpuRo3Fgx9vmdzqWMiONglVOZSyypG1CyPqLzpgA+pnIzvv1Q1sA 2MfiCw0E1SEHYZPVCnxntXUd0B4gSEFjuvWOnH0n6921wN3gBn8erm0itnGBBDoO1hRc CwHjOX4sfVUKBRiXkgniCx4ji++E3kTPkas76WFasFdJLTipuYhjjxCF8o+Qdbe+FkYv LGVg== X-Gm-Message-State: AOAM531V9gspqWxrEhO3+7rxPPN7KcSeKeVgIOHSipFphvocaZewjlOL pBoSs6Qc2dW6hByfA/oqWHPn7HhLUqyScYcZ7uur0obfupqsHDzaj+M= 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" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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