Return-path: Received: from mail-yk0-f181.google.com ([209.85.160.181]:36668 "EHLO mail-yk0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750726AbcBHJzI (ORCPT ); Mon, 8 Feb 2016 04:55:08 -0500 Received: by mail-yk0-f181.google.com with SMTP id z7so84692621yka.3 for ; Mon, 08 Feb 2016 01:55:08 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <1454920723-48071-1-git-send-email-nbd@openwrt.org> From: Krishna Chaitanya Date: Mon, 8 Feb 2016 15:24:48 +0530 Message-ID: (sfid-20160208_105513_616840_65FF7AA2) Subject: Re: [RFC v4] mac80211: add A-MSDU tx support To: Emmanuel Grumbach Cc: Felix Fietkau , linux-wireless , Johannes Berg Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, Feb 8, 2016 at 2:56 PM, Emmanuel Grumbach wrote: > On Mon, Feb 8, 2016 at 10:38 AM, Felix Fietkau wrote: >> Requires software tx queueing support. frag_list support (for zero-copy) >> is optional. >> >> Signed-off-by: Felix Fietkau >> --- > > > Ok - looks fine, but... and here comes the hard stuff. > The frame size in the PLCP is limited in a way that you can't - from a > spec POV - enable A-MSDU for low rates. Of course, you don't want to > do that for low rates at all regardless of the spec. > Since you build the A-MSDU in the mac80211 Tx queue which is not aware > of the link quality, how do we prevent A-MSDU if the rate is low / > dropping. > I'd even argue that when the rates get lower, you'll have more > packets piling up in the software queue and ... even more chance to > get A-MSDU in the exact case where you really want to avoid it? Similar to triggering AMPDU setup, we should put this control in RC (minstrel) to start/stop AMSDU based on link quality/if the rates drop below a pre-defined MCS (or) only for best-throughput rates.