From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f70.google.com (mail-pl0-f70.google.com [209.85.160.70]) by kanga.kvack.org (Postfix) with ESMTP id A83796B0006 for ; Fri, 20 Jul 2018 17:06:32 -0400 (EDT) Received: by mail-pl0-f70.google.com with SMTP id q18-v6so8310208pll.3 for ; Fri, 20 Jul 2018 14:06:32 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id x82-v6sor825283pfe.150.2018.07.20.14.06.30 for (Google Transport Security); Fri, 20 Jul 2018 14:06:30 -0700 (PDT) Date: Sat, 21 Jul 2018 00:06:26 +0300 From: "Kirill A. Shutemov" 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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