From mboxrd@z Thu Jan 1 00:00:00 1970 From: linas@austin.ibm.com (Linas Vepstas) Subject: Re: RFC: issues concerning the next NAPI interface Date: Fri, 24 Aug 2007 11:51:10 -0500 Message-ID: <20070824165110.GH4282@austin.ibm.com> References: <200708241559.17055.ossthema@de.ibm.com> <20070824153703.GN5592@sgi.com> <200708241747.16592.ossthema@de.ibm.com> <20070824085203.42f4305c@freepuppy.rosehill.hemminger.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan-Bernd Themann , Thomas Klein , Marcus@ozlabs.org, Jan-Bernd Themann , netdev , linux-kernel , Christoph Raisch , linux-ppc , akepner@sgi.com, Eder , Stefan Roscher To: Stephen Hemminger Return-path: Received: from e32.co.us.ibm.com ([32.97.110.150]:32908 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759693AbXHXQvN (ORCPT ); Fri, 24 Aug 2007 12:51:13 -0400 Content-Disposition: inline In-Reply-To: <20070824085203.42f4305c@freepuppy.rosehill.hemminger.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Aug 24, 2007 at 08:52:03AM -0700, Stephen Hemminger wrote: > > You need hardware support for deferred interrupts. Most devices have it (e1000, sky2, tg3) > and it interacts well with NAPI. It is not a generic thing you want done by the stack, > you want the hardware to hold off interrupts until X packets or Y usecs have expired. Just to be clear, in the previous email I posted on this thread, I described a worst-case network ping-pong test case (send a packet, wait for reply), and found out that a deffered interrupt scheme just damaged the performance of the test case. Since the folks who came up with the test case were adamant, I turned off the defferred interrupts. While defferred interrupts are an "obvious" solution, I decided that they weren't a good solution. (And I have no other solution to offer). --linas