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, 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 BDC30C63697 for ; Tue, 17 Nov 2020 19:45:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4021A2463B for ; Tue, 17 Nov 2020 19:45:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4021A2463B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 282726B0036; Tue, 17 Nov 2020 14:45:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2317B6B005C; Tue, 17 Nov 2020 14:45:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0D4036B0068; Tue, 17 Nov 2020 14:45:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0241.hostedemail.com [216.40.44.241]) by kanga.kvack.org (Postfix) with ESMTP id D13786B0036 for ; Tue, 17 Nov 2020 14:45:25 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 6360B3626 for ; Tue, 17 Nov 2020 19:45:25 +0000 (UTC) X-FDA: 77494939410.02.ocean80_4a09aa427334 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin02.hostedemail.com (Postfix) with ESMTP id 4136710097AA1 for ; Tue, 17 Nov 2020 19:45:25 +0000 (UTC) X-HE-Tag: ocean80_4a09aa427334 X-Filterd-Recvd-Size: 2669 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Tue, 17 Nov 2020 19:45:24 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 00F9FABDE; Tue, 17 Nov 2020 19:45:23 +0000 (UTC) MIME-Version: 1.0 Date: Tue, 17 Nov 2020 20:45:21 +0100 From: Oscar Salvador To: Muchun Song Cc: "Song Bao Hua (Barry Song)" , corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org, oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, almasrymina@google.com, rientjes@google.com, willy@infradead.org, mhocko@suse.com, duanxiongchun@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [External] RE: [PATCH v4 00/21] Free some vmemmap pages of hugetlb page In-Reply-To: References: <20201113105952.11638-1-songmuchun@bytedance.com> <349168819c1249d4bceea26597760b0a@hisilicon.com> <714ae7d701d446259ab269f14a030fe9@hisilicon.com> User-Agent: Roundcube Webmail Message-ID: X-Sender: osalvador@suse.de Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit 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 2020-11-17 17:29, Muchun Song wrote: > Now for the 2MB HugrTLB page, we only free 6 vmemmap pages. > But your words woke me up. Maybe we really can free 7 vmemmap > pages. In this case, we can see 8 of the 512 struct page structures > has beed set PG_head flag. If we can adjust compound_head() > slightly and make compound_head() return the real head struct > page when the parameter is the tail struct page but with PG_head > flag set. I will start an investigation and a test. I would not overcomplicate things at this stage, but rather keep it simple as the code is already tricky enough(without counting the LOC thatvit adds). We can always build on top later on in order to improve things. -- Oscar Salvador SUSE L3