Return-path: Received: from mail-pv0-f174.google.com ([74.125.83.174]:33084 "EHLO mail-pv0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750863Ab1FUUKz (ORCPT ); Tue, 21 Jun 2011 16:10:55 -0400 Received: by pvg12 with SMTP id 12so78770pvg.19 for ; Tue, 21 Jun 2011 13:10:54 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <4DFA2989.10503@candelatech.com> Date: Tue, 21 Jun 2011 23:10:54 +0300 Message-ID: (sfid-20110621_221057_793321_F6C7C7F8) Subject: Re: Help on AMPDU stuck in transmit queue From: Emmanuel Grumbach To: Chaoxing Lin Cc: Ben Greear , "ath9k-devel@lists.ath9k.org" , "linux-wireless@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Tue, Jun 21, 2011 at 19:16, Chaoxing Lin wrote: > > Anybody,any ideas/comments? > > Here is my update. > > I tried 2.6.39.1. The situation gets better, but not fixed completely. The ping packets still lose (about 62 seconds) once a while. > I say "gets better" because it recovers. > > The ping session recovers after about 62 seconds which matches to 2 NULL data packet interval. I sniffed the air, it looks like every 31 seconds, a NULL data packet is sent out from client. > > > Again, the symptom does not happen when 802.11n is disabled on AP. > > Can anyone explain or help? > > Below is my ping session info (message on console) > Can you please try to send the pings with AC != BE. I saw once a bug related to ampdu reordering buffer. NULL packets would enter the reordering buffer and mess up the counters there. Since the reordering buffer is tid-wise, trying with another AC may help to understand. I assume that QoS NULL data packets are sent as BE. The fact that the ping recovers after a while may be explained by the wrap around of the sequence. This is a really wild guess... but sometimes it can hit....