From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lennert Buytenhek Subject: Re: [E1000-devel] Transmission limit Date: Sat, 4 Dec 2004 11:36:26 +0100 Message-ID: <20041204103626.GA17872@xi.wantstofly.org> References: <1101484740.24742.213.camel@mellia.lipar.polito.it> <41A76085.7000105@draigBrady.com> <1101499285.1079.45.camel@jzny.localdomain> <16811.8052.678955.795327@robur.slu.se> <1101821501.1043.43.camel@jzny.localdomain> <20041130134600.GA31515@xi.wantstofly.org> <1101824754.1044.126.camel@jzny.localdomain> <20041201001107.GE4203@xi.wantstofly.org> <1101863399.4663.54.camel@sfeldma-mobl.dsl-verizon.net> <20041203205706.GC9808@xi.wantstofly.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: jamal , Robert Olsson , P@draigBrady.com, mellia@prezzemolo.polito.it, e1000-devel@lists.sourceforge.net, Jorge Manuel Finochietto , Giulio Galante , netdev@oss.sgi.com Return-path: To: Scott Feldman Content-Disposition: inline In-Reply-To: <20041203205706.GC9808@xi.wantstofly.org> Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org On Fri, Dec 03, 2004 at 09:57:06PM +0100, Lennert Buytenhek wrote: > > My problem is I only have a P4 desktop system with a 82544 nic running > > at PCI 32/33Mhz, so I can't play with the big boys. But, attached is a > > rework of the Tx path to eliminate 1) Tx interrupts, and 2) Tx > > descriptor write-backs. For me, I see a nice jump in kpps, but I'd like > > others to try with their setups. We should be able to get to wire speed > > with 60-byte packets. > > Attached is a graph of my numbers with and without your patch for: > - An 82540 at PCI 32/33, idle 33MHz card on the same bus forcing it to 33MHz. > - An 82541 at PCI 32/66. > - An 82546 at PCI-X 64/100, NIC can do 133MHz but mobo only does 100MHz. When extrapolating these numbers to the 0-byte packet case (which then tells you the per-packet overhead), I get the following approximate numbers: case overhead phi-32-33-82540-2.6.9 1.86 us phi-32-66-82541-2.6.9 1.41 us phi-64-100-82546-2.6.9 1.45 us phi-32-33-82540-2.6.9-feldman 1.48 us phi-32-66-82541-2.6.9-feldman 1.13 us phi-64-100-82546-2.6.9-feldman 1.25 us Note that this figure doesn't differ all that much between the different bus widths/speeds. In any case, if I ever want to get more than ~880kpps on this hardware, there's no other way than to make this overhead go down. For saturating 1Gb/s with 60B packets on 64/100, the overhead can't be more than ~0.59 us per packet or you lose. --L