From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: NAPI, e100, and system performance problem Date: Fri, 22 Apr 2005 13:36:56 +0200 Message-ID: References: <1113855967.7436.39.camel@localhost.localdomain> <20050419055535.GA12211@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Arthur Kepner , "Brandeburg, Jesse" , netdev@oss.sgi.com, davem@redhat.com Return-path: To: Greg Banks In-Reply-To: <20050419055535.GA12211@sgi.com> (Greg Banks's message of "Tue, 19 Apr 2005 15:55:35 +1000") Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org Greg Banks writes: > > An inordinate amount of CPU is being spent running around polling the > device instead of dealing with the packets in IP, TCP and NFS land. > By inordinate, we mean twice as much or more cpu% than a MIPS/Irix > box with slower CPUs. We have seen similar behaviour. With NAPI some benchmarks run a lot slower than on a driver on the same hardware/NIC without NAPI. This can be even observed with simple tests like netperf single stream between two boxes. There seems to be also some problems with bidirectional traffic, although I have not fully tracked them down to NAPI yet. There is definitely some problem in NAPI land ... -Andi