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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 5322FC43461 for ; Tue, 15 Sep 2020 14:33:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D6B1322261 for ; Tue, 15 Sep 2020 14:33:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="isoDWDZi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D6B1322261 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 235806B00DA; Tue, 15 Sep 2020 10:33:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1BFAF6B00DB; Tue, 15 Sep 2020 10:33:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 086DE6B00DC; Tue, 15 Sep 2020 10:33:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0121.hostedemail.com [216.40.44.121]) by kanga.kvack.org (Postfix) with ESMTP id E327D6B00DA for ; Tue, 15 Sep 2020 10:33:12 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 9094612E9 for ; Tue, 15 Sep 2020 14:33:12 +0000 (UTC) X-FDA: 77265538224.24.power86_20066db27112 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id 600D31A4A5 for ; Tue, 15 Sep 2020 14:33:12 +0000 (UTC) X-HE-Tag: power86_20066db27112 X-Filterd-Recvd-Size: 2684 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf21.hostedemail.com (Postfix) with ESMTP for ; Tue, 15 Sep 2020 14:33:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=N/RImaBnXFF3qV4mVIQ9BHL7AM45ePKA2LT5MfLcY7k=; b=isoDWDZijETKPcfACECD40iTGj m7dtS99gUE2YIdQKRNawehnEMFycuNrpgVmgOUXa4i3mmp2Cg2XAJvGFO9sj1F9b5LGGrznkLNgp3 dfra5s1A6jdc2AcvbDqdrtty9bgFwY2fDoLoon1Te/Znm8tdIgGXGr5VZZOMwZRh0/whuaClyUie+ DX3kDpFozwg/jmJHVFaSZ9QR1de+PsLEW6LxzrpjMaJU/9NkKiBbafGAOjQXeZoyR51HXGXQ4mWre ytCoB0y+jPqTEjVZ8jcsclL+LfcnX9bc+6OYQwoWHC2Gj+p0Aax5KQ4ovoyXxrhbNY09DGfXA79YC nAXUeo3w==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kIC0f-00065s-HW; Tue, 15 Sep 2020 14:32:42 +0000 Date: Tue, 15 Sep 2020 15:32:41 +0100 From: Matthew Wilcox 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, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH 00/24] mm/hugetlb: Free some vmemmap pages of hugetlb page Message-ID: <20200915143241.GH5449@casper.infradead.org> References: <20200915125947.26204-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200915125947.26204-1-songmuchun@bytedance.com> X-Rspamd-Queue-Id: 600D31A4A5 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 Tue, Sep 15, 2020 at 08:59:23PM +0800, Muchun Song wrote: > This patch series will free some vmemmap pages(struct page structures) > associated with each hugetlbpage when preallocated to save memory. It would be lovely to be able to do this. Unfortunately, it's completely impossible right now. Consider, for example, get_user_pages() called on the fifth page of a hugetlb page. I've spent a lot of time thinking about this, and there's a lot of work that needs to happen before we can do this, mostly in device drivers. Do you want to help? It's a multi-year project.