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 19CD83B2A4 for ; Fri, 18 Oct 2019 09:48:20 -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 1iLSc4-00045S-Vf; Fri, 18 Oct 2019 15:48:17 +0200 Message-ID: <9fc60b546b54b40357264d67536733251cf39ebe.camel@sipsolutions.net> From: Johannes Berg To: Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= , Kan Yan Cc: linux-wireless@vger.kernel.org, make-wifi-fast@lists.bufferbloat.net, ath10k@lists.infradead.org, John Crispin , Lorenzo Bianconi , Felix Fietkau , Rajkumar Manoharan , Kevin Hayes Date: Fri, 18 Oct 2019 15:48:13 +0200 In-Reply-To: <87imomdvsj.fsf@toke.dk> References: <157115993755.2500430.12214017471129215800.stgit@toke.dk> <157115993866.2500430.13989567853855880476.stgit@toke.dk> <87sgnqe4wg.fsf@toke.dk> <10b885b3238cede2d99c6134bebcc0c8ba6f6b10.camel@sipsolutions.net> <87imomdvsj.fsf@toke.dk> 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 v2 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: Fri, 18 Oct 2019 13:48:20 -0000 On Fri, 2019-10-18 at 15:31 +0200, Toke Høiland-Jørgensen wrote: > Well, let's try to do the actual math... A full-size (1538 bytes) packet > takes ~2050 microseconds to transmit at 6 Mbps. Adding in overhead, it's > certainly still less that 4096 us, so 12 bits is plenty. What about A-MSDUs? But I guess maximum continous transmissions are at most 4ms anyway, so a single packet should never be longer. > That leaves > four bits for the ACK status ID if we just split the u16; if we only > ever have "a handful", that should be enough, no? It's how many are in flight at a time, 16 doesn't seem likely to happen, but I don't really know what applications are doing with it now. Probably only wpa_s for the EAPOL TX status. > We could also split 5/11. That would support up to 32 ACK IDs, and we > can just truncate the airtime at 2048 us, which is not a big deal I'd > say. We can also play with the units of the airtime, e.g. making that a multiple of 2 or 4 us? Seems unlikely to matter much? > Think it mostly depends on what is the smallest ID space for ACK IDs we > can live with? :) :) TBH, I don't really know. In a lot of hardware using this is really bad for performance so it shouldn't be used much, so ... johannes