From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-ew0-f214.google.com ([209.85.219.214]:47233 "EHLO mail-ew0-f214.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754134AbZHGQzl (ORCPT ); Fri, 7 Aug 2009 12:55:41 -0400 Received: by ewy10 with SMTP id 10so1673447ewy.37 for ; Fri, 07 Aug 2009 09:55:41 -0700 (PDT) From: Ivo van Doorn To: Johannes Berg Subject: Re: [PATCH] mac80211: allow DMA optimisation Date: Fri, 7 Aug 2009 18:55:38 +0200 Cc: John Linville , "linux-wireless" References: <1249656135.7194.6.camel@johannes.local> In-Reply-To: <1249656135.7194.6.camel@johannes.local> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Message-Id: <200908071855.38921.IvDoorn@gmail.com> Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi, > If we have a lot of frames to transmit at once, for > instance with fragmentation, it can be an optimisation > to only tell the DMA engine about them on the last > fragment/frame to avoid banging the IO too much. This > patch allows implementation such an optimisation by > telling the driver when more frames can be expected. Wouldn't this be the same as the if (ieee80211_has_morefrags()) .. kick queue ... Other then that this flag is very nice, I already had some similar sort of mechanism build into rt2x00 based on RTS/CTS and ieee80211_has_morefrags() > Currently, this is used by mac80211 only on fragmented > frames, but could also be used in the future on other > frames when the queue was full and there are multiple > frames pending. > > Note that drivers need to be careful when using this > flag, they need to kick their DMA engines not just > when this flag is clear, but also when the queue gets > full so that progress can be made. What would a good value be for the threshold? rt2x00 currently uses 10% of the queue, which means that 2 or 3 entries are kept available at all times. Ivo