From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: RFC: issues concerning the next NAPI interface Date: Sun, 26 Aug 2007 18:58:15 -0700 (PDT) Message-ID: <20070826.185815.93042514.davem@davemloft.net> References: <46CF127D.1090609@katalix.com> <20070824.144711.18301866.davem@davemloft.net> <46D1D634.7060007@katalix.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: shemminger@linux-foundation.org, ossthema@de.ibm.com, akepner@sgi.com, netdev@vger.kernel.org, raisch@de.ibm.com, themann@de.ibm.com, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, meder@de.ibm.com, tklein@de.ibm.com, stefan.roscher@de.ibm.com To: jchapman@katalix.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:42080 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753266AbXH0B6R (ORCPT ); Sun, 26 Aug 2007 21:58:17 -0400 In-Reply-To: <46D1D634.7060007@katalix.com> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: James Chapman Date: Sun, 26 Aug 2007 20:36:20 +0100 > David Miller wrote: > > From: James Chapman > > Date: Fri, 24 Aug 2007 18:16:45 +0100 > > > >> Does hardware interrupt mitigation really interact well with NAPI? > > > > It interacts quite excellently. > > If NAPI disables interrupts and keeps them disabled while there are more > packets arriving or more transmits being completed, why do hardware > interrupt mitigation / coalescing features of the network silicon help? Because if your packet rate is low enough such that the cpu can process the interrupt fast enough and thus only one packet gets processed per NAPI poll, the cost of going into and out of NAPI mode dominates the packet processing costs.