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=-2.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_MED, USER_AGENT_NEOMUTT 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 CB794ECDFBB for ; Fri, 20 Jul 2018 21:06:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8679E20671 for ; Fri, 20 Jul 2018 21:06:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="mnR+9dLr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8679E20671 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shutemov.name 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 S1728459AbeGTV4b (ORCPT ); Fri, 20 Jul 2018 17:56:31 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:41544 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727749AbeGTV4b (ORCPT ); Fri, 20 Jul 2018 17:56:31 -0400 Received: by mail-pg1-f194.google.com with SMTP id z8-v6so7812729pgu.8 for ; Fri, 20 Jul 2018 14:06:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=1lSBfmdyStY+qeBaFCgSb+R+TLH/5rDIp+TRXUtl+ls=; b=mnR+9dLrvHCdDN5gXwzlMCk2BKSY/zQADiR6bz3jTOIcUTgb31B6tqDwxmEsCWRsF0 FXvhjJ1lMUdy5n39LcYWgybTA+rk9VTBNFuw9vTX2PEuffMsVgFv5poZ34ETmyDhTX+n VCe8QLU3T3MN+/pz/zKMf9C8/7yXp7QQHcAMd0TCHM69UyMlXrkYdCqkf30/oAwz52+K mwLeLSkXIZFCt41Tx148ih5uPUJVUYzJn6LCGD26ZxEEvkhMe+slhwEGal/CcNuDNaLU bn4TkzxvKvzt3qDWzK4oBNNE492Zqz0jvS07KEcFm9SDxsRzzNVTEeK9043O4cB7jxV3 6Qpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=1lSBfmdyStY+qeBaFCgSb+R+TLH/5rDIp+TRXUtl+ls=; b=caNTGPXPqZ6D26cyShxKOaM6t7ZkVBFrToxXdFTZan/r0LCeAZdX+79OjruWSvKzS7 by2H7vcdkBikcp9cL6rD3K4uuyRKtWjFPPLg7vYjrnacGGNs8tHXOgUPzpB6wffNTxhN jybEER7qi+x56PJmQ9ALPuVUTOxA1jmF6lD4YPF2Y0iNDwU+cMiJ49jVepG/icIV+GKe 3SK8LOQgmglKiT8EXG76jnxdS8EVU3BMlsDZ2PclsFX28YLaCynlInFqdHooL/rZMYPp 6rorCh/GM9a1cSm0+qOaPpcMnxuMH6A0FHk/w5NMciLf4t9AOVNt4AlCzpp138bQiDgG l/lw== X-Gm-Message-State: AOUpUlFlB67+SEPXZ6PZEz3Gx9C1WuuyQfZl9PhAPbmFqdAFg6ss8N5w 3Ku6FSUCnU0eoYyc0Hy3JAEUNQ== X-Google-Smtp-Source: AAOMgpdaKFcz2DPWSAPD0DvVj6kXKg42crJpv5hde8j71pGCrrhYb17gm74e2zpIXdq8lSV+EmkLEg== X-Received: by 2002:a62:c98e:: with SMTP id l14-v6mr3682602pfk.10.1532120790564; Fri, 20 Jul 2018 14:06:30 -0700 (PDT) Received: from kshutemo-mobl1.localdomain ([134.134.139.83]) by smtp.gmail.com with ESMTPSA id v17-v6sm3539787pfn.177.2018.07.20.14.06.29 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Jul 2018 14:06:29 -0700 (PDT) Received: by kshutemo-mobl1.localdomain (Postfix, from userid 1000) id 7321B300254; Sat, 21 Jul 2018 00:06:26 +0300 (+03) Date: Sat, 21 Jul 2018 00:06:26 +0300 From: "Kirill A. Shutemov" To: Yang Shi Cc: hughd@google.com, rientjes@google.com, aaron.lu@intel.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: thp: remove use_zero_page sysfs knob Message-ID: <20180720210626.5bnyddmn4avp2l3x@kshutemo-mobl1> References: <1532110430-115278-1-git-send-email-yang.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1532110430-115278-1-git-send-email-yang.shi@linux.alibaba.com> User-Agent: NeoMutt/20180622 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 21, 2018 at 02:13:50AM +0800, Yang Shi wrote: > By digging into the original review, it looks use_zero_page sysfs knob > was added to help ease-of-testing and give user a way to mitigate > refcounting overhead. > > It has been a few years since the knob was added at the first place, I > think we are confident that it is stable enough. And, since commit > 6fcb52a56ff60 ("thp: reduce usage of huge zero page's atomic counter"), > it looks refcounting overhead has been reduced significantly. > > Other than the above, the value of the knob is always 1 (enabled by > default), I'm supposed very few people turn it off by default. > > So, it sounds not worth to still keep this knob around. I don't think that having the knob around is huge maintenance burden. And since it helped to workaround a security bug relative recently I would rather keep it. -- Kirill A. Shutemov