From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-31-ewr.dyndns.com (mxout-022-ewr.mailhop.org [216.146.33.22]) by lists.bufferbloat.net (Postfix) with ESMTP id 7FCFD2E0392 for ; Tue, 15 Mar 2011 15:53:11 -0700 (PDT) Received: from scan-32-ewr.mailhop.org (scan-32-ewr.local [10.0.141.238]) by mail-31-ewr.dyndns.com (Postfix) with ESMTP id CF66F6F8991 for ; Tue, 15 Mar 2011 22:53:10 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 209.85.161.43 Received: from mail-fx0-f43.google.com (mail-fx0-f43.google.com [209.85.161.43]) by mail-31-ewr.dyndns.com (Postfix) with ESMTP id ECA1A6F88C1 for ; Tue, 15 Mar 2011 22:53:05 +0000 (UTC) Received: by fxm3 with SMTP id 3so1378743fxm.16 for ; Tue, 15 Mar 2011 15:53:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:subject:from:to:cc:in-reply-to:references :content-type:date:message-id:mime-version:x-mailer :content-transfer-encoding; bh=pISQNV8iamk/HseNZk5IKuFokwEGd/e/SSaXfbkjzn8=; b=SyFugqWryaP53w9HWNCC7+K51iN7tXtJGfFoCnfa5NaCK5dhU5n3gUuWA2OKSQgRNO 0PSKje2/Z4XHuBl2EvUqv79oVQpf5/8NXR1p0bt9Td079Ar+KSqFjCAHjDOLjE2QqTYH fIHqz5QOogtvEummJ/+jVEb9PenQ9Yr3lru+I= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=ETt+N3oc/fffHLTzDo+8EO1o9tr5BbHUkq0ShOw32qzNBOCnvspx5OCOufl6Dv6GDN 9elFtNS6kqJeE6Uaz9OJj1UXqD1pm30rcs6ZG4+t7Yh98acD1lBIkKo2twL5IT4qWzLK mJNzj6yt2LXj04QHo+HmTdDhMV/M5u2wvTQe0= Received: by 10.223.58.80 with SMTP id f16mr65074fah.148.1300229585227; Tue, 15 Mar 2011 15:53:05 -0700 (PDT) Received: from [192.168.1.21] (167.237.66-86.rev.gaoland.net [86.66.237.167]) by mx.google.com with ESMTPS id n2sm173218fam.4.2011.03.15.15.53.03 (version=SSLv3 cipher=OTHER); Tue, 15 Mar 2011 15:53:04 -0700 (PDT) From: Eric Dumazet To: rick.jones2@hp.com In-Reply-To: <1300228592.2087.2191.camel@tardy> 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> Content-Type: text/plain; charset="UTF-8" Date: Tue, 15 Mar 2011 23:52:58 +0100 Message-ID: <1300229578.2565.29.camel@edumazet-laptop> 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 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 22:53:11 -0000 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 ? 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)