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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham 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 089CDECDFB8 for ; Mon, 23 Jul 2018 21:52:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA37820854 for ; Mon, 23 Jul 2018 21:52:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AA37820854 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388298AbeGWW4G (ORCPT ); Mon, 23 Jul 2018 18:56:06 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:51183 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388158AbeGWW4F (ORCPT ); Mon, 23 Jul 2018 18:56:05 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R461e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01355;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0T5BsF0c_1532382764; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0T5BsF0c_1532382764) by smtp.aliyun-inc.com(127.0.0.1); Tue, 24 Jul 2018 05:52:47 +0800 Subject: Re: [PATCH] mm: thp: remove use_zero_page sysfs knob To: David Rientjes Cc: "Kirill A. Shutemov" , hughd@google.com, aaron.lu@intel.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1532110430-115278-1-git-send-email-yang.shi@linux.alibaba.com> <20180720210626.5bnyddmn4avp2l3x@kshutemo-mobl1> <3118b646-681e-a2aa-dc7b-71d4821fa50f@linux.alibaba.com> From: Yang Shi Message-ID: <91caed46-6437-a137-0dbc-dadd113f8d58@linux.alibaba.com> Date: Mon, 23 Jul 2018 14:52:43 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/23/18 1:31 PM, David Rientjes wrote: > On Fri, 20 Jul 2018, Yang Shi wrote: > >> I agree to keep it for a while to let that security bug cool down, however, if >> there is no user anymore, it sounds pointless to still keep a dead knob. >> > It's not a dead knob. We use it, and for reasons other than > CVE-2017-1000405. To mitigate the cost of constantly compacting memory to > allocate it after it has been freed due to memry pressure, we can either > continue to disable it, allow it to be persistently available, or use a > new value for use_zero_page to specify it should be persistently > available. My understanding is the cost of memory compaction is *not* unique for huge zero page, right? It is expected when memory pressure is met, even though huge zero page is disabled.