Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264219AbTEOUoS (ORCPT ); Thu, 15 May 2003 16:44:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264231AbTEOUoS (ORCPT ); Thu, 15 May 2003 16:44:18 -0400 Received: from rwcrmhc52.attbi.com ([216.148.227.88]:5512 "EHLO rwcrmhc52.attbi.com") by vger.kernel.org with ESMTP id S264219AbTEOUoR (ORCPT ); Thu, 15 May 2003 16:44:17 -0400 Message-ID: <3EC3FF1C.7090202@mvista.com> Date: Thu, 15 May 2003 15:57:00 -0500 From: Corey Minyard User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3) Gecko/20030313 X-Accept-Language: en-us, en MIME-Version: 1.0 To: "Feldman, Scott" CC: LKML Subject: Re: Problem with e100 driver and latency on different packet sizes References: In-Reply-To: X-Enigmail-Version: 0.74.0.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1484 Lines: 47 Thanks for the response. I looked at the code, and there doesn't seem to be a way to turn it off dynamically or with a bootline option. I have to have the driver compiled into the kernel (because I'm netbooting with NFS) so I can't really use a module parameter. A dynamic field in /proc would be quite nice. -Corey Feldman, Scott wrote: >>I've attached a small program to measure latency of >>round-trip time on UDP. If I send 85-byte packets between >>two of my machines, I get 170us round-trip latency. If I >>send 86-byte packets, I get 1329us latency. >>This seems quite odd. If I test on the eepro100 driver, I >>get expected linear increase in round-trip time as the packet >>size increases, and it never gets close to 1300us. >> >> > >This sounds like a side-effect of the "CPU Cycle Saver" feature to >bundle Rx packets per one interrupt. See >Documentation/networking/e100.txt. I haven't tried your setup, but I >would guess that you can play around with the BundleSmallFr module >parameter, or better yet, if you want the lowest latencies, turn off CPU >Saver (ucode=0). > >CPU Saver trades latency for reduced interrupts, resulting in CPU >savings, hence the name. > >Hope this helps. > >-scott > > > > - 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/