From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:191:4433::2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id AEB133B2A4 for ; Tue, 1 Oct 2019 04:45:02 -0400 (EDT) Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.92.2) (envelope-from ) id 1iFDmF-0002cH-8N; Tue, 01 Oct 2019 10:44:59 +0200 Message-ID: From: Johannes Berg To: Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= Cc: linux-wireless@vger.kernel.org, make-wifi-fast@lists.bufferbloat.net, John Crispin , Lorenzo Bianconi , Felix Fietkau Date: Tue, 01 Oct 2019 10:44:58 +0200 In-Reply-To: <156889576534.191202.17686228416284995279.stgit@alrua-x1> References: <156889576422.191202.5906619710809654631.stgit@alrua-x1> <156889576534.191202.17686228416284995279.stgit@alrua-x1> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: Re: [Make-wifi-fast] [PATCH RFC/RFT 1/4] mac80211: Rearrange ieee80211_tx_info to make room for tx_time_est X-BeenThere: make-wifi-fast@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 Oct 2019 08:45:02 -0000 Hi, Sorry for the long time to review here ... On Thu, 2019-09-19 at 14:22 +0200, Toke Høiland-Jørgensen wrote: > From: Toke Høiland-Jørgensen > > To implement airtime queue limiting, we need to keep a running account of > the estimated airtime of all skbs queued into the device. Do to this > correctly, we need to store the airtime estimate into the skb so we can > decrease the outstanding balance when the skb is freed. This means that the > time estimate must be stored somewhere that will survive for the lifetime > of the skb. > > Fortunately, we had a couple of bytes left in the 'status' field in the > ieee80211_tx_info; and since we only plan to calculate the airtime estimate > after the skb is dequeued from the FQ structure, on the control side we can > share the space with the codel enqueue time. And by rearranging the order > of elements it is possible to have the position of the new tx_time_est line > up between the control and status structs, so the value will survive from > when mac80211 hands the packet to the driver, and until the driver either > frees it, or hands it back through TX status. Seems reasonable to me, if we end up needing it and don't have an out- of-band path (that you seem to have been discussing in this long thread too) johannes