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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 7BD99C433DB for ; Thu, 7 Jan 2021 11:16:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D9A2223125 for ; Thu, 7 Jan 2021 11:16:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D9A2223125 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0E9A68D0132; Thu, 7 Jan 2021 06:16:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0A16F8D011F; Thu, 7 Jan 2021 06:16:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EA1E58D0132; Thu, 7 Jan 2021 06:16:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0200.hostedemail.com [216.40.44.200]) by kanga.kvack.org (Postfix) with ESMTP id D49408D011F for ; Thu, 7 Jan 2021 06:16:47 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 8436B181AEF30 for ; Thu, 7 Jan 2021 11:16:47 +0000 (UTC) X-FDA: 77678726454.27.swim44_1910a93274e9 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 688473D663 for ; Thu, 7 Jan 2021 11:16:47 +0000 (UTC) X-HE-Tag: swim44_1910a93274e9 X-Filterd-Recvd-Size: 2475 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Thu, 7 Jan 2021 11:16:46 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1610018205; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=POfkAesmWAxZFM/w8qK4CkNJ8RSs5M/EPAXMtQXTlo0=; b=sux/5aXvVkemPDQckX+/nlpFPLNBtIrZn6aifH1txN/GKlcef9lYMVcHJhEc2xBVNQjqY6 hgewmCmUrSaX6kZKlxpWi6UAiAHZAE+3zACFevBrglj5sKPj7qi840QK9s1WBAGjzSIllg gl//9gNZp7qAVHWYQBEGTrOH5riTxXw= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B3970AFD7; Thu, 7 Jan 2021 11:16:45 +0000 (UTC) Date: Thu, 7 Jan 2021 12:16:42 +0100 From: Michal Hocko To: Muchun Song Cc: Mike Kravetz , Andrew Morton , Naoya Horiguchi , Andi Kleen , Linux Memory Management List , LKML , Yang Shi Subject: Re: [External] Re: [PATCH v2 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one Message-ID: <20210107111642.GF13207@dhcp22.suse.cz> References: <20210106084739.63318-1-songmuchun@bytedance.com> <20210106084739.63318-2-songmuchun@bytedance.com> <20210106161327.GR13207@dhcp22.suse.cz> 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 Thu 07-01-21 10:52:21, Muchun Song wrote: > 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. I am not as worried as I would like to see some actual justification for this optimization. -- Michal Hocko SUSE Labs