From owner-freebsd-stable@FreeBSD.ORG Tue Aug 17 19:55:12 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E16131065673 for ; Tue, 17 Aug 2010 19:55:12 +0000 (UTC) (envelope-from jfvogel@gmail.com) Received: from mail-ew0-f54.google.com (mail-ew0-f54.google.com [209.85.215.54]) by mx1.freebsd.org (Postfix) with ESMTP id 6C92D8FC15 for ; Tue, 17 Aug 2010 19:55:11 +0000 (UTC) Received: by ewy26 with SMTP id 26so4002327ewy.13 for ; Tue, 17 Aug 2010 12:55:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:cc:content-type; bh=0IsMyrs2NyDkfiIyTFarJ4djPN9m5VvEKiuJgBFqOQ8=; b=AugaH0RSrorhpNufeOoc7bT/90N2j1uk5vLgOkp39c5zAqyHabyKy6jc7D3U5NsRGV FQH28kNs9UGuRka3WUBpXMQjq7vGOLXji5YwlTgtQzb0RCEvKghpYqpivBMvdmw07tlR 0iTKgsJFB8HC1TZ3UfelXWfsoeyAEY7wH0gio= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=tXnX8QiS/s33iA7uJ33qcFZH8UJenPnk+4kX5vDYCZIwABSDnZLYXcR/3aAWUBk7D6 rdlUsMT95tRNKpsKCw1vSXe3ExRAAIvgaQwuV8cGYP6KqLWkLbxp0yq9D53pOluN8ry/ Q/kG2Q0hPMMxHM1tEQ/HXq6ojs1mYhNATajoA= MIME-Version: 1.0 Received: by 10.216.3.83 with SMTP id 61mr1149407weg.110.1282074910955; Tue, 17 Aug 2010 12:55:10 -0700 (PDT) Received: by 10.216.48.6 with HTTP; Tue, 17 Aug 2010 12:55:08 -0700 (PDT) In-Reply-To: <20100817194705.GD6482@michelle.cdnetworks.com> References: <201006102031.o5AKVCH2016467@lava.sentex.ca> <201007021739.o62HdMOU092319@lava.sentex.ca> <20100702193654.GD10862@michelle.cdnetworks.com> <201008162107.o7GL76pA080191@lava.sentex.ca> <20100817185208.GA6482@michelle.cdnetworks.com> <20100817191420.GB6482@michelle.cdnetworks.com> <20100817194705.GD6482@michelle.cdnetworks.com> Date: Tue, 17 Aug 2010 12:55:08 -0700 Message-ID: From: Jack Vogel To: pyunyh@gmail.com Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-stable@freebsd.org Subject: Re: RELENG_7 em problems (and RELENG_8) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 17 Aug 2010 19:55:13 -0000 The guy who worries about the Linux driver's performance is in my team, and he's a very good engineer, and we're talking about the hardware's DMA, so its not an OS issue, thus I'm not saying I'm sure, but I'm dubious about this, at least when we're talking about igb. But hey, I'm willing to be proven wrong :) Jack On Tue, Aug 17, 2010 at 12:47 PM, Pyun YongHyeon wrote: > On Tue, Aug 17, 2010 at 12:34:31PM -0700, Jack Vogel wrote: > > I believe the requirement of a context descriptor for most frames in the > igb > > driver > > is just the way the hardware works, I've looked over the Linux driver > again > > and it > > looks like they require the same. I don't believe its a big deal, just > the > > added > > descriptor for the frame. > > > > Setting up context does not cost much. The real cost comes from > stopping requesting DMA for next packet whenever a new context > is written. > AFAIK Linux always added a new checksum context. I don't know > whether Linux cares about the cost of refilling pipeline or > measured the performance differences. FreeBSD noticed the > difference on em(4) controllers and took appropriate action to take > full advantage of the hardware feature, I think. > I have to experiment how igb(4) works when it is told to reuse > configured context(both checksum and TSO context). > >