From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] Re: KVM call agenda for Apr 27 Date: Tue, 27 Apr 2010 08:21:20 -0500 Message-ID: <4BD6E4D0.1030905@codemonkey.ws> References: <20100426172634.GC15278@x200.localdomain> <4BD5D28C.7080700@codemonkey.ws> <20100426221258.GH15278@x200.localdomain> <4BD61584.9080208@codemonkey.ws> <4BD6A61C.3010100@redhat.com> <4BD6E229.60501@codemonkey.ws> <4BD6E41E.7070106@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Chris Wright , qemu-devel@nongnu.org, kvm@vger.kernel.org To: Kevin Wolf Return-path: Received: from mail-qy0-f179.google.com ([209.85.221.179]:57951 "EHLO mail-qy0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755723Ab0D0NVZ (ORCPT ); Tue, 27 Apr 2010 09:21:25 -0400 Received: by qyk9 with SMTP id 9so19312571qyk.1 for ; Tue, 27 Apr 2010 06:21:24 -0700 (PDT) In-Reply-To: <4BD6E41E.7070106@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 04/27/2010 08:18 AM, Kevin Wolf wrote: > > The watermark is not some complex computed value, but actually the > statistic itself. We can get rid of handling a threshold in qemu by just > signalling "something has changed with this stat". > > I'm really not arguing that qemu should do anything complex or even > define policy. It's just about avoiding polling all the time when > nothing has changed and polling too late when things are changing quickly. > > >> Polling is really the right solution. It gives the management tool >> ultimate flexibility in tweaking the heuristics as they see fit. >> > Isn't providing this flexibility completely orthogonal to polling vs. > event-based? > Except then we need to offer a generic statistics mechanism which seems like it's going to add a fair bit of complexity. So far, the only argument for it seems to be a misplaced notion that "polling is evil". Regards, Anthony Liguori > Kevin >