From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id 09BAE6B0253 for ; Thu, 14 Sep 2017 17:21:44 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id e64so1184449wmi.0 for ; Thu, 14 Sep 2017 14:21:43 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id s74si721872wmb.175.2017.09.14.14.21.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Sep 2017 14:21:43 -0700 (PDT) Date: Thu, 14 Sep 2017 14:21:40 -0700 From: Andrew Morton Subject: Re: [PATCH -mm -v4 3/5] mm, swap: VMA based swap readahead Message-Id: <20170914142140.9c5e3ef37e6bad1d68899e64@linux-foundation.org> In-Reply-To: <20170914131446.GA12850@bgram> References: <20170807054038.1843-1-ying.huang@intel.com> <20170807054038.1843-4-ying.huang@intel.com> <20170913014019.GB29422@bbox> <20170913140229.8a6cad6f017fa3ea8b53cefc@linux-foundation.org> <20170914075345.GA5533@bbox> <87h8w5jxph.fsf@yhuang-dev.intel.com> <20170914131446.GA12850@bgram> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: "Huang, Ying" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner , Rik van Riel , Shaohua Li , Hugh Dickins , Fengguang Wu , Tim Chen , Dave Hansen On Thu, 14 Sep 2017 22:14:46 +0900 Minchan Kim wrote: > > Now. Users can choose between VMA based readahead and original > > readahead via a knob as follow at runtime, > > > > /sys/kernel/mm/swap/vma_ra_enabled > > It's not a config option and is enabled by default. IOW, it's under the radar > so current users cannot notice it. That's why we want to emit big fat warnning. > when old user set 0 to page-cluster. However, as Andrew said, it's lame. > > If we make it config option, product maker/kernel upgrade user can have > a chance to notice and read description so they could be aware of two weird > knobs and help to solve the problem in advance without printk_once warn. > If user has no interest about swap-readahead or skip the new config option > by mistake, it works physcial readahead which means no regression. Yup, a Kconfig option sounds like a good idea. And that's a bit more friendly to tiny kernels as well. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org