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From devnull@lkml.org Thu Jun 13 18:42:56 2024 Delivery-date: Mon, 24 Apr 2006 20:14:02 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751073AbWDXSMa (ORCPT ); Mon, 24 Apr 2006 14:12:30 -0400 Received: from spirit.analogic.com ([204.178.40.4]:27910 "EHLO spirit.analogic.com") by vger.kernel.org with ESMTP id S1751076AbWDXSM2 convert rfc822-to-8bit (ORCPT ); Mon, 24 Apr 2006 14:12:28 -0400 Received: from chaos.analogic.com ([10.112.50.11]) by phoenix.analogic.com with Microsoft SMTPSVC(6.0.3790.211); Mon, 24 Apr 2006 14:12:19 -0400 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Received: from chaos.analogic.com (localhost [127.0.0.1]) by chaos.analogic.com (8.12.11/8.12.11) with ESMTP id k3OICI2T024288; Mon, 24 Apr 2006 14:12:18 -0400 X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0 Received: (from linux-os@localhost) by chaos.analogic.com (8.12.11/8.12.11/Submit) id k3OIC1oH024287; Mon, 24 Apr 2006 14:12:01 -0400 In-Reply-To: <444D08A8.3060908@hp.com> X-OriginalArrivalTime: 24 Apr 2006 18:12:19.0094 (UTC) FILETIME=[9FEF1B60:01C667CA] content-class: urn:content-classes:message Subject: Re: Van Jacobson's net channels and real-time Date: Mon, 24 Apr 2006 14:12:01 -0400 Message-Id: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: Van Jacobson's net channels and real-time Thread-Index: AcZnyp/4IMYJKnXkQ4SSdtdHpBAmoQ== References: <200604221529.59899.ioe-lkml@rameria.de> <20060422134956.GC6629@wohnheim.fh-wedel.de> <200604230205.33668.ioe-lkml@rameria.de> <444CFFE5.1020509@intel.com> To: "Rick Jones" Cc: "Auke Kok" , "Ingo Oeser" , =?iso-8859-1?Q?J=F6rn_Engel?= , "Ingo Oeser" , "David S. Miller" , , Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 24 Apr 2006, Rick Jones wrote: >>>> Thats right. This will be made a non issue with early demuxing >>>> on the NIC and MSI (or was it MSI-X?) which will select >>>> the right CPU based on hardware channels. >>> >>> MSI-X. with MSI you still have only one cpu handling all MSI interrupts and >>> that doesn't look any different than ordinary interrupts. MSI-X will allow >>> much better interrupt handling across several cpu's. >>> >>> Auke >>> - >> >> >> Message signaled interrupts are just a kudge to save a trace on a >> PC board (read make junk cheaper still). They are not faster and >> may even be slower. They will not be the salvation of any interrupt >> latency problems. The solutions for increasing networking speed, >> where the bit-rate on the wire gets close to the bit-rate on the >> bus, is to put more and more of the networking code inside the >> network board. The CPU get interrupted after most things (like >> network handshakes) are complete. > > if the issue is bus vs network bitrates would offloading really buy that > much? i suppose that for minimum sized packets not DMA'ing the headers > across the bus would be a decent win, but down at small packet sizes > where headers would be 1/3 to 1/2 the stuff DMA'd around, I would think > one is talking more about CPU path lengths than bus bitrates. > > and up and "full size" segments, since everyone is so fond of bulk > transfer tests, the transfer saved by not shovig headers across the bus > is what 54/1448 or ~3.75% > > spreading interrupts via MSI-X seems nice and all, but i keep wondering > if the header field-based distribution that is (will be) done by the > NICs is putting the cart before the horse - should the NIC essentially > be telling the system the CPU on which to run the application, or should > the CPU on which the application runs be telling "networking" where it > should be happening? > > rick jones > Ideally, TCP/IP is so mature that one should be able to tell some hardware state-machine "Connect with 123.555.44.333, port 23" and it signals via interrupt when that happens. Then one should be able to say "send these data to that address" or "fill this buffer with data from that address". All the networking could be done on the board, perhaps with a dedicated CPU (as is now done) or all in silicon. So, the driver end of the networking software just handles buffers. There are interrupts that show status such as completions or time-outs, trivial stuff. Cheers, Dick Johnson Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips). Warning : 98.36% of all statistics are fiction, book release in April. _  **************************************************************** The information transmitted in this message is confidential and may be privileged. Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited. 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