From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH NET] e1000e: Change wthresh to 1 to avoid possible Tx stalls Date: Wed, 10 Oct 2012 23:00:00 -0400 (EDT) Message-ID: <20121010.230000.1520707219906312743.davem@davemloft.net> References: <20121011013420.30383.27700.stgit@jbrandeb-snb.jf.intel.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, shimoda.hiroaki@gmail.com, eric.dumazet@gmail.com, therbert@google.com To: jesse.brandeburg@intel.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:58972 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750952Ab2JKDAC (ORCPT ); Wed, 10 Oct 2012 23:00:02 -0400 In-Reply-To: <20121011013420.30383.27700.stgit@jbrandeb-snb.jf.intel.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Jesse Brandeburg Date: Wed, 10 Oct 2012 18:34:20 -0700 > From: Hiroaki SHIMODA > > This patch originated from Hiroaki SHIMODA but has been modified > by Intel with some minor cleanups and additional commit log text. > > Denys Fedoryshchenko and others reported Tx stalls on e1000e with > BQL enabled. Issue was root caused to hardware delays. They were > introduced because some of the e1000e hardware with transmit > writeback bursting enabled, waits until the driver does an > explict flush OR there are WTHRESH descriptors to write back. > > Sometimes the delays in question were on the order of seconds, > causing visible lag for ssh sessions and unacceptable tx > completion latency, especially for BQL enabled kernels. > > To avoid possible Tx stalls, change WTHRESH back to 1. > > The current plan is to investigate a method for re-enabling > WTHRESH while not harming BQL, but those patches will be later > for net-next if they work. > > please enqueue for stable since v3.3 as this bug was introduced in > commit 3f0cfa3bc11e7f00c9994e0f469cbc0e7da7b00c > Author: Tom Herbert > Date: Mon Nov 28 16:33:16 2011 +0000 > > e1000e: Support for byte queue limits > > Changes to e1000e to use byte queue limits. > > Reported-by: Denys Fedoryshchenko > Tested-by: Denys Fedoryshchenko > Signed-off-by: Hiroaki SHIMODA > CC: eric.dumazet@gmail.com > CC: therbert@google.com > Signed-off-by: Jesse Brandeburg Applied and queued up for -stable, thanks.