From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH] emulate accessed bit for EPT Date: Fri, 5 Feb 2010 15:34:23 -0200 Message-ID: <20100205173422.GA14706@amt.cnet> References: <20100203161103.11e2b572@annuminas.surriel.com> <20100204041212.GI19641@balbir.in.ibm.com> <4B6ACE5B.9080601@redhat.com> <20100204174715.GL5959@random.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Rik van Riel , balbir@linux.vnet.ibm.com, jdike@addtoit.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, avi@redhat.com To: Andrea Arcangeli Return-path: Content-Disposition: inline In-Reply-To: <20100204174715.GL5959@random.random> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Thu, Feb 04, 2010 at 06:47:15PM +0100, Andrea Arcangeli wrote: > On Thu, Feb 04, 2010 at 08:40:43AM -0500, Rik van Riel wrote: > > I suspect it won't be very many. I have been monitoring > > /proc/meminfo on my system while testing this patch, and > > it is quite typical that the size of the inactive anon > > list does not change for minutes at a time. > > > > In other words, no pages are moved onto or off of the > > inactive anon list for several minutes. That corresponds > > to a very small number of minor faults introduced by my > > patch. > > When there's light VM pressure, ideally there should be zero overhead > caused by the patch. When there is VM pressure this will avoid some > unnecessary I/O which should outweight the minor faults. It should be > a good default behavior. Agree. But perhaps a module parameter to turn accessed bit emulation off might be handy in the future?