From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sunset.davemloft.net (unknown [74.93.104.97]) by ozlabs.org (Postfix) with ESMTP id D6B67DE004 for ; Mon, 27 Aug 2007 11:58:18 +1000 (EST) Date: Sun, 26 Aug 2007 18:58:15 -0700 (PDT) Message-Id: <20070826.185815.93042514.davem@davemloft.net> To: jchapman@katalix.com Subject: Re: RFC: issues concerning the next NAPI interface From: David Miller In-Reply-To: <46D1D634.7060007@katalix.com> 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 Cc: tklein@de.ibm.com, themann@de.ibm.com, stefan.roscher@de.ibm.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, raisch@de.ibm.com, linuxppc-dev@ozlabs.org, akepner@sgi.com, meder@de.ibm.com, ossthema@de.ibm.com, shemminger@linux-foundation.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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.