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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 2374DC4361B for ; Thu, 17 Dec 2020 15:00:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A74B823975 for ; Thu, 17 Dec 2020 15:00:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A74B823975 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 B185D6B006E; Thu, 17 Dec 2020 10:00:06 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AA0D06B0070; Thu, 17 Dec 2020 10:00:06 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9DE3F6B0071; Thu, 17 Dec 2020 10:00:06 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0156.hostedemail.com [216.40.44.156]) by kanga.kvack.org (Postfix) with ESMTP id 860EB6B006E for ; Thu, 17 Dec 2020 10:00:06 -0500 (EST) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 5E40D8249980 for ; Thu, 17 Dec 2020 15:00:05 +0000 (UTC) X-FDA: 77603084370.01.pull30_39163e927435 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id 29F51100473C7 for ; Thu, 17 Dec 2020 15:00:04 +0000 (UTC) X-HE-Tag: pull30_39163e927435 X-Filterd-Recvd-Size: 2380 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Thu, 17 Dec 2020 15:00:04 +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 99214AD29; Thu, 17 Dec 2020 15:00:02 +0000 (UTC) Date: Thu, 17 Dec 2020 15:59:58 +0100 From: Oscar Salvador To: Muchun Song Cc: 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, song.bao.hua@hisilicon.com, david@redhat.com, naoya.horiguchi@nec.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: [PATCH v10 00/11] Free some vmemmap pages of HugeTLB page Message-ID: <20201217145953.GA13874@linux> References: <20201217121303.13386-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201217121303.13386-1-songmuchun@bytedance.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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, Dec 17, 2020 at 08:12:52PM +0800, Muchun Song wrote: > In this case, for the 1GB HugeTLB page, we can save 4088 pages(There are > 4096 pages for struct page structs, we reserve 2 pages for vmemmap and 8 > pages for page tables. So we can save 4088 pages). This is a very substantial > gain. On our server, run some SPDK/QEMU applications which will use 1024GB > hugetlbpage. With this feature enabled, we can save ~16GB(1G hugepage)/~11GB > (2MB hugepage, the worst case is 10GB while the best is 12GB) memory. Is the above really true? We no longer need to allocate pagetables, so the savings go up to 4094, right? I will be off for a few days but I expect to get back to this and review the missing bits when I am back. -- Oscar Salvador SUSE L3