Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030418AbVIAVqu (ORCPT ); Thu, 1 Sep 2005 17:46:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030417AbVIAVqu (ORCPT ); Thu, 1 Sep 2005 17:46:50 -0400 Received: from mf01.sitadelle.com ([212.94.174.68]:53132 "EHLO smtp.cegetel.net") by vger.kernel.org with ESMTP id S1030419AbVIAVqs (ORCPT ); Thu, 1 Sep 2005 17:46:48 -0400 Message-ID: <431776C5.9070709@cosmosbay.com> Date: Thu, 01 Sep 2005 23:46:45 +0200 From: Eric Dumazet User-Agent: Mozilla Thunderbird 1.0 (Windows/20041206) X-Accept-Language: fr, en MIME-Version: 1.0 To: Rick Warner Cc: linux-kernel@vger.kernel.org, eliot@microway.com Subject: Re: latency doubled on tg3 device from 2.6.11 to 2.6.12 References: <200509011730.51990.rick@microway.com> In-Reply-To: <200509011730.51990.rick@microway.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1573 Lines: 41 Rick Warner a ?crit : > Hello, > We have been testing latency and bandwidth using our proprietary MPI link > checker tool (http://www.microway.com/mpilinkchecker.html) and have found > that the latency increased from ~25ms to ~45ms going from 2.6.11 to 2.6.12. > 2.6.13 has the same result. We also tried the latest bcm5700 from broadcom > (8.2.18) and got the same ~45ms latencies. This was tried on several > different opteron and em64t motherboards. > > We see 20-25ms latencies with the e1000 driver (with some module options) on > all 3 kernel versions. For those interested, the e1000 options used are: > > InterruptThrottleRate=0 RxIntDelay=0 TxIntDelay=0 RxAbsIntDelay=0 > TxAbsIntDelay=0 > > Digging through source, it seems that a new locking mechanism for tg3 was put > in place in 2.6.12. Is this the likely cause? What can we do to restore our > lower latency? > > Could you please define latency ? tg3 driver was recently updated to use coalescing. So when the nic receives one frame, it may delay up to XXXX us ( XXXX < 1024) the interrupt. But 25 ms is far more than 1024 us, so I dont think this coalescing can explain your problem. The HZ change from 1000 to 250 could be the root of the problem ? Using a simple ping between 2 machines with tg3, I get less than 1ms time. Eric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/