From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Bizon Subject: Re: [PATCH ver2] Avoid enqueuing skb for default qdiscs Date: Mon, 01 Feb 2010 15:16:34 +0100 Message-ID: <1265033794.32192.54.camel@sakura.staff.proxad.net> References: <20090806114421.19208.39374.sendpatchset@localhost.localdomain> <1265017940.32192.23.camel@sakura.staff.proxad.net> Reply-To: mbizon@freebox.fr Mime-Version: 1.0 Content-Type: text/plain; charset="ANSI_X3.4-1968" Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, herbert@gondor.apana.org.au, Jarek Poplawski , kaber@trash.net, netdev@vger.kernel.org To: Krishna Kumar2 Return-path: Received: from smtp6-g21.free.fr ([212.27.42.6]:46793 "EHLO smtp6-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753297Ab0BAOQo (ORCPT ); Mon, 1 Feb 2010 09:16:44 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2010-02-01 at 19:12 +0530, Krishna Kumar2 wrote: Hi, > sch_direct_xmit can be called from dev_queue_xmit for a > stopped device only if the device had xmit the previous > skb, stopped the device and returned OK. Then the next Yes, that's what happen in my case. > BTW, I don't think this patch would change the earlier > behavior. The old code would have done the same thing. Oh, my mistake then. I always thought the requeue counter was indicating the driver returned TX_BUSY (and failed to stop the queue before), which is not polite. If the current behavior is the expected one, then there is no problem here. > As I explained, this should happen only once per stop event. > Could you tell which driver is having this problem? Is it > waking up too early, eg, it might be stopping when the hw tx > descriptor is full but waking up when a few slots open up, > and those will get filled up immediately on fast systems. > Then you will see a lot of requeue's. This is an atm driver which is not mainlined. The system is not that fast, but the link is (very) slow (< 1 Mbit/s). The driver is waking up the queue once the hardware queue is not full anymore (at least one free tx desc), and the free slot gets filled immediately since the link is slow. Thanks for explaining ! -- Maxime