From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: via-rhine interrupts Date: Thu, 19 Aug 2010 19:09:12 +0200 Message-ID: <20100819170912.GA2387@del.dom.local> References: <20100815200431.GA4993@del.dom.local> <20100818.234939.71574087.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: ruzicka.jakub@gmail.com, netdev@vger.kernel.org To: David Miller Return-path: Received: from mail-bw0-f46.google.com ([209.85.214.46]:45812 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752391Ab0HSRJY (ORCPT ); Thu, 19 Aug 2010 13:09:24 -0400 Received: by bwz11 with SMTP id 11so1366950bwz.19 for ; Thu, 19 Aug 2010 10:09:22 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20100818.234939.71574087.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Aug 18, 2010 at 11:49:39PM -0700, David Miller wrote: > From: Jarek Poplawski > Date: Sun, 15 Aug 2010 22:04:31 +0200 > > > I've just tested it using a simplistic patch below, which skips > > some napi receiving by doing it only every second jiffie (on even > > ones), and I've got around 30% less interrupts from via-rhine, > > which seems to suggest napi works OK, but there is too low > > traffic (or too fast soft interrupt handling) to affect hard > > interrupts. (Btw, probably CONFIG_HZ can matter here a bit too. > > I tested with 1000.) > > 100Mbit on any modern system isn't going to trigger NAPI much at all > even with near full link utilization. > > The simply cpu processes the packets too fast for them to gather up > much at all. > > Some improvement in polling could be gained if the via-rhine has some > HW interrupt mitigation settings. However after a quick perusal of > the driver I don't see anything about this. The mitigation ethtool > ops aren't implemented either, so I'm not optimistic :-) > Yes, now I see the old comments (pre 2.6.27) mentioned 10kpps threshold, which wasn't reached in Jakub's example. http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=32b0f53e5bc80b87fd20d4d78a0e0cb602c9157a Jarek P.