From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: [PATCH] net: increase receive packet quantum Date: Mon, 3 Nov 2008 13:03:03 -0800 Message-ID: <20081103130303.29dd4e21@extreme> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: David Miller Return-path: Received: from mail.vyatta.com ([76.74.103.46]:40396 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754002AbYKCVDG (ORCPT ); Mon, 3 Nov 2008 16:03:06 -0500 Sender: netdev-owner@vger.kernel.org List-ID: This patch gets about 1.25% back on tbench regression. My change to NAPI for multiqueue support changed the time limit on network receive processing. Under sustained loads like tbench, this can cause the receiver to reschedule prematurely. Signed-off-by: Stephen Hemminger --- a/net/core/dev.c 2008-11-03 11:11:44.000000000 -0800 +++ b/net/core/dev.c 2008-11-03 11:16:07.000000000 -0800 @@ -2373,7 +2373,7 @@ EXPORT_SYMBOL(__napi_schedule); static void net_rx_action(struct softirq_action *h) { struct list_head *list = &__get_cpu_var(softnet_data).poll_list; - unsigned long start_time = jiffies; + unsigned long time_limit = jiffies + 2; int budget = netdev_budget; void *have; @@ -2384,13 +2384,10 @@ static void net_rx_action(struct softirq int work, weight; /* If softirq window is exhuasted then punt. - * - * Note that this is a slight policy change from the - * previous NAPI code, which would allow up to 2 - * jiffies to pass before breaking out. The test - * used to be "jiffies - start_time > 1". + * Allow this to run for 2 jiffies since which will allow + * an average latency of 1.5/HZ. */ - if (unlikely(budget <= 0 || jiffies != start_time)) + if (unlikely(budget <= 0 || time_after(jiffies, time_limit))) goto softnet_break; local_irq_enable();