From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752969Ab0JGQV2 (ORCPT ); Thu, 7 Oct 2010 12:21:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3572 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752353Ab0JGQV0 (ORCPT ); Thu, 7 Oct 2010 12:21:26 -0400 Message-ID: <4CADF365.3080406@redhat.com> Date: Thu, 07 Oct 2010 18:20:53 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc13 Thunderbird/3.1.4 MIME-Version: 1.0 To: Gleb Natapov CC: Marcelo Tosatti , Gleb Natapov , kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mingo@elte.hu, a.p.zijlstra@chello.nl, tglx@linutronix.de, hpa@zytor.com, riel@redhat.com, cl@linux-foundation.org Subject: Re: [PATCH v6 04/12] Add memory slot versioning and use it to provide fast guest write interface References: <1286207794-16120-1-git-send-email-gleb@redhat.com> <1286207794-16120-5-git-send-email-gleb@redhat.com> <20101005165738.GA32750@amt.cnet> <20101006111417.GX11145@redhat.com> <20101006143847.GB31423@amt.cnet> <20101006200836.GC4120@minantech.com> <4CAD9A2D.7020009@redhat.com> <20101007154248.GA30949@amt.cnet> <20101007160340.GD4120@minantech.com> In-Reply-To: <20101007160340.GD4120@minantech.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/07/2010 06:03 PM, Gleb Natapov wrote: > > > > > > Isn't SET_USER_MEMORY_REGION so slow that calling it 2^32 times > > > isn't really feasible? > > > > Assuming it takes 1ms, it would take 49 days. > > > We may fail ioctl when max value is reached. The question is how much slot > changes can we expect from real guest during its lifetime. > A normal guest has a 30 Hz timer for reading the vga framebuffer, multiple slots. Let's assume 100 Hz frequency, that gives 490 days until things stop working. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.