From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e32.co.us.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTP id DF149DDF1C for ; Sat, 25 Aug 2007 02:51:15 +1000 (EST) Date: Fri, 24 Aug 2007 11:51:10 -0500 To: Stephen Hemminger Subject: Re: RFC: issues concerning the next NAPI interface 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 In-Reply-To: <20070824085203.42f4305c@freepuppy.rosehill.hemminger.net> From: linas@austin.ibm.com (Linas Vepstas) Cc: Thomas Klein , Jan-Bernd Themann , netdev , linux-kernel , Christoph Raisch , linux-ppc , Jan-Bernd Themann , Eder , akepner@sgi.com, Stefan Roscher , Marcus@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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