From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-14-iad.dyndns.com (mxout-089-iad.mailhop.org [216.146.32.89]) by lists.bufferbloat.net (Postfix) with ESMTP id F3D202E0271 for ; Tue, 15 Mar 2011 16:03:04 -0700 (PDT) Received: from scan-11-iad.mailhop.org (scan-11-iad.local [10.150.0.208]) by mail-14-iad.dyndns.com (Postfix) with ESMTP id 32A1F44A8A7 for ; Tue, 15 Mar 2011 23:03:03 +0000 (UTC) X-Spam-Score: -4.0 (----) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 15.216.28.36 Received: from g1t0029.austin.hp.com (g1t0029.austin.hp.com [15.216.28.36]) by mail-14-iad.dyndns.com (Postfix) with ESMTP id D0A8644A7C7 for ; Tue, 15 Mar 2011 23:03:02 +0000 (UTC) Received: from g1t0038.austin.hp.com (g1t0038.austin.hp.com [16.236.32.44]) by g1t0029.austin.hp.com (Postfix) with ESMTP id 6255438381; Tue, 15 Mar 2011 23:03:02 +0000 (UTC) Received: from [16.89.244.213] (tardy.cup.hp.com [16.89.244.213]) by g1t0038.austin.hp.com (Postfix) with ESMTP id F3FB33021E; Tue, 15 Mar 2011 23:03:01 +0000 (UTC) From: Rick Jones To: Eric Dumazet In-Reply-To: <1300229578.2565.29.camel@edumazet-laptop> References: <4D7F4121.40307@freedesktop.org> <20110315175942.GA10064@goldfish> <1300212877.2087.2155.camel@tardy> <20110315183111.GB2542@tuxdriver.com> <29B06777-CC5F-4802-8727-B04F58CDA9E3@gmail.com> <20110315205146.GF2542@tuxdriver.com> <219C7840-ED79-49EA-929D-96C5A6200401@gmail.com> <20110315151946.31e86b46@nehalam> <1300228592.2087.2191.camel@tardy> <1300229578.2565.29.camel@edumazet-laptop> Content-Type: text/plain; charset="UTF-8" Date: Tue, 15 Mar 2011 16:02:54 -0700 Message-ID: <1300230174.2087.2201.camel@tardy> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 8bit Cc: Stephen Hemminger , bloat@lists.bufferbloat.net Subject: Re: [Bloat] Random idea in reaction to all the discussion of TCP flavours - timestamps? X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list Reply-To: rick.jones2@hp.com List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Mar 2011 23:03:05 -0000 On Tue, 2011-03-15 at 23:52 +0100, Eric Dumazet wrote: > Le mardi 15 mars 2011 à 15:36 -0700, Rick Jones a écrit : > > Back and forth synchronization between driver and device is > > doubleplusungood. Being able to remove a packet on the tx queue already > > made known to the NIC sounds like it could become a rathole. If you are > > lucky, you *might* have a "valid/invalid" bit in a packet descriptor > > that the driver could hope to set before the NIC had pulled-in a copy > > across the I/O bus. > > There are two different use cases : > > 1) Wired devices, where we want to push more 10+ Gbps, so we can assume > a posted skb is transmitted immediately. Even a basic qdisc can be a > performance bottleneck. Set TX ring size to 256 or 1024+ buffers to > avoid taking too many interrupts. > > 2) wireless, were typical bandwidth is small enough we can afford a > qdisc with a trafic shaper, good flow classification, whatever limit on > "maximum waiting time in qdisc queue or drop it" and a very small queue > on hardware ? So, I've no worries that my home system has plenty of "oomph" for fancy things when speaking over wireless, but that is a desktop. How much "oomph" relative to wireless bandwidth exists in hand-helds? Right now I think of "wireless" as being, in essence, 100BTto1GbE (wild handwaving) - do the CPUs in handhelds possess that much more "oomph" than "regular" systems did when 100BT or 1GbE first appeared? rick jones > > In both cases, we dont need to "cancel" a packet post to NIC hardware, > or we need special hardware support (some NICS already provide hardware > TX completion times) > >