From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH] kvm tools: Add MMIO coalescing support Date: Sat, 4 Jun 2011 13:27:43 +0200 Message-ID: <20110604112743.GA24146@elte.hu> References: <1307130668-5652-1-git-send-email-levinsasha928@gmail.com> <20110604093847.GB14524@elte.hu> <1307182441.7239.2.camel@lappy> <20110604101711.GB16292@elte.hu> <1307183318.7239.6.camel@lappy> <20110604103508.GE16292@elte.hu> <20110604104712.GG16292@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Sasha Levin , penberg@kernel.org, kvm@vger.kernel.org, asias.hejun@gmail.com, gorcunov@gmail.com, prasadjoshi124@gmail.com To: Alexander Graf Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:54464 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756207Ab1FDL1s (ORCPT ); Sat, 4 Jun 2011 07:27:48 -0400 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: * Alexander Graf wrote: > > So? I only inquired about latencies, asking what impact on > > latencies is. Regardless of the circumstances we do not want to > > introduce unbound latencies. > > > > If there are no unbound latencies then i'm happy. > > Sure, I'm just saying that the mechanism was invented for > unmodified guests :). Well, but that does not excuse the introduction of unbound latencies. (if those latencies are introduced here - i don't know, i'm asking.) > > Well, since user-space gets the MMIOs only once the guest exits > > it's not independent, is it? > > If we don't know when a guest ends an MMIO stream, we can't > optimize it. Period. [...] But that's no excuse. If you cannot optimize them without unnacceptable collateral damage then don't optimize it then. That's why i asked what the damage is - if there's any damage. Thanks, Ingo