From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karsten Desler Subject: Re: _High_ CPU usage while routing (mostly) small UDP packets Date: Wed, 8 Dec 2004 14:08:45 +0100 Message-ID: <20041208130845.GA5036@soohrt.org> References: <20041206205305.GA11970@soohrt.org> <20041206134849.498bfc93.davem@davemloft.net> <20041206224107.GA8529@soohrt.org> <41B58A58.8010007@draigBrady.com> <20041207112139.GA3610@soohrt.org> <20041208053953.GC17946@alpha.home.local> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Cc: P@draigBrady.com, "David S. Miller" , netdev@oss.sgi.com, linux-kernel@vger.kernel.org Return-path: To: Willy Tarreau Content-Disposition: inline In-Reply-To: <20041208053953.GC17946@alpha.home.local> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org * Willy Tarreau wrote: > On Tue, Dec 07, 2004 at 12:21:39PM +0100, Karsten Desler wrote: > > > > I also notice that a lot of time is spent allocating > > > and freeing the packet buffers (and possible hidden > > > time due to cache misses due to allocating on one > > > CPU and freeing on another?). > > > How many [RT]xDescriptors do you have configured by the way? > > > > 256. I increased them to 1024 shortly after the profiling run, but > > didn't notice any change in the cpu usage (will try again with cyclesoak). > > Have you checked the interrupts rate ? I had an e1000 eating many CPU cycles > because it would generate 50000 interrupts/s. Passing the module > InterruptThrottleRate=5000 definitely calmed it down, and more than doubled > the data rate. I was running mit ITR=3000, but as a test to see if NAPI works, I disabled ITR on eth0 bringing the int/s rate up to 50k. Is that normal? I always though NAPI was supposed to kick in way earlier. Anyways, I'm going to try different ITR settings to see if they make any difference. Cheers, Karsten