Return-path: Received: from mail-ew0-f219.google.com ([209.85.219.219]:46821 "EHLO mail-ew0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755235Ab0AES3F (ORCPT ); Tue, 5 Jan 2010 13:29:05 -0500 Received: by ewy19 with SMTP id 19so8745152ewy.21 for ; Tue, 05 Jan 2010 10:29:03 -0800 (PST) To: Lennert Buytenhek Cc: linux-wireless@vger.kernel.org Subject: Re: infinite transmit buffering issue in 2.6.32 mac80211 References: <20100105083803.GP1735@mail.wantstofly.org> From: Kalle Valo Date: Tue, 05 Jan 2010 20:29:00 +0200 In-Reply-To: <20100105083803.GP1735@mail.wantstofly.org> (Lennert Buytenhek's message of "Tue\, 5 Jan 2010 09\:38\:03 +0100") Message-ID: <87eim4v21f.fsf@purkki.valot.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-wireless-owner@vger.kernel.org List-ID: Lennert Buytenhek writes: > Hi! Hello, > Since "mac80211: remove master netdev", mac80211 no longer propagates > TX queue full status (ieee80211_stop_queue et al) up. While the > underlying hardware's TX queue is stopped, mac80211 buffers frames > internally (in ieee80211_tx), but there's no upper limit on the number > of frames it will buffer, leading to badness when there is heavy TX > traffic on the wireless interface: We have noticed very strange throughput degration both with wl1251 and wl1271. With 2.6.28 both drivers were able to achieve 10 Mbit/s throughput over TCP, but with 2.6.32 (and almost the same drivers) we get less than 4 Mbit/s. Because we see it both with wl1251 and wl1271, we are starting to suspect that it's a problem in mac80211. We haven't started analysing this yet, but I'm hoping someone from our team to start it soon. I have no idea if our problem is related to the problem Lennert reports or not, but we will definitely try Johannes' patch and see if it helps. -- Kalle Valo