From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753458Ab1LLRXf (ORCPT ); Mon, 12 Dec 2011 12:23:35 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:49708 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751261Ab1LLRXe (ORCPT ); Mon, 12 Dec 2011 12:23:34 -0500 Date: Mon, 12 Dec 2011 18:21:48 +0100 From: Ingo Molnar To: Sasha Levin Cc: Alan Cox , Thomas Gleixner , Pekka Enberg , LKML Subject: Re: [patch 0/3] kvm tool: Serial emulation overhaul Message-ID: <20111212172148.GD23870@elte.hu> References: <20111210132220.083204833@linutronix.de> <20111211103047.GA19299@elte.hu> <20111212102750.469f0d9f@pyramind.ukuu.org.uk> <1323687592.16450.0.camel@lappy> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1323687592.16450.0.camel@lappy> User-Agent: Mutt/1.5.21 (2010-09-15) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Sasha Levin wrote: > > You can emulate a chip with a 64byte or so FIFO. You can do > > I/O cycle prediction in the kernel part and you can use the > > empty bit as a clue (which is what most serial<->ethernet > > widgetry does). > > The performance problems here aren't the same performance > problems you have on real hardware. The problem here is that > it costs 40k cycles for the guest to access the emulated chip. I question that 40k cycles figure - where does Marcelo's paper mention it? Thanks, Ingo