From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263112AbTDQGtr (ORCPT ); Thu, 17 Apr 2003 02:49:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263111AbTDQGtr (ORCPT ); Thu, 17 Apr 2003 02:49:47 -0400 Received: from isis.cs3-inc.com ([207.224.119.73]:23798 "EHLO isis.cs3-inc.com") by vger.kernel.org with ESMTP id S263103AbTDQGtp (ORCPT ); Thu, 17 Apr 2003 02:49:45 -0400 Date: Wed, 16 Apr 2003 23:56:45 -0700 Message-Id: <200304170656.h3H6ujA28940@isis.cs3-inc.com> From: don-linux@isis.cs3-inc.com (Don Cohen) To: linux-kernel@vger.kernel.org, linux-net@vger.kernel.org Subject: proposed optimization for network drivers Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I notice that netif_rx (net/core/dev.c) discards packets when it's in throttle mode. However, before it does this the driver has already wasted a lot of time allocating the skb, calling eth_type_trans, etc. That effort could be saved if the driver checked throttle first. Sample diff: --- /usr/src/linux-2.4.18-clean/drivers/net/8139too.c Mon Feb 25 11:37:59 2002 +++ /usr/src/linux-2.4.18/drivers/net/8139too.c Wed Apr 16 23:30:30 2003 @@ -1908,6 +1908,11 @@ return; } + if (softnet_data[smp_processor_id()].throttle) { + dev->last_rx = jiffies; + netdev_rx_stat[smp_processor_id()].dropped++; + } else { + /* Malloc up new buffer, compatible with net-2e. */ /* Omit the four octet CRC from the length. */ @@ -1936,6 +1941,7 @@ dev->name); tp->stats.rx_dropped++; } + } cur_rx = (cur_rx + rx_size + 4 + 3) & ~3; RTL_W16 (RxBufPtr, cur_rx - 16); Hmm, now that I notice, there is one small change in semantics here. Before every packet that was counted by netdev_rx_stat[].dropped had also been counted in stats.rx_bytes and rx_packets and this is no longer the case. If that bothers you then perhaps there should just be a separate counter for packets dropped like this. In my limited experimentation this sort of change has significantly increased the number of packets I could process when they were arriving too fast. Please cc me on replies.