From owner-freebsd-hackers Fri Sep 28 11:35: 4 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from whizzo.transsys.com (whizzo.TransSys.COM [144.202.42.10]) by hub.freebsd.org (Postfix) with ESMTP id 1348037B40C for ; Fri, 28 Sep 2001 11:35:01 -0700 (PDT) Received: from whizzo.transsys.com (#6@localhost.transsys.com [127.0.0.1]) by whizzo.transsys.com (8.11.4/8.11.4) with ESMTP id f8SIYdZ77174; Fri, 28 Sep 2001 14:34:39 -0400 (EDT) (envelope-from louie@whizzo.transsys.com) Message-Id: <200109281834.f8SIYdZ77174@whizzo.transsys.com> X-Mailer: exmh version 2.5 07/13/2001 with nmh-1.0.4 To: Andrew Gallatin Cc: tlambert2@mindspring.com, Jonathan Lemon , the_srinivas@hotmail.com, hackers@FreeBSD.ORG X-Image-URL: http://www.transsys.com/louie/images/louie-mail.jpg From: "Louis A. Mamakos" Subject: timestamp offload [was Re: TCP&IP cksum offload on FreeBSD 4.2] References: <200109270157.f8R1vZ546863@prism.flugsvamp.com> <3BB42E50.B32F5E95@mindspring.com> <15284.32914.874966.260722@grasshopper.cs.duke.edu> In-reply-to: Your message of "Fri, 28 Sep 2001 09:52:18 EDT." <15284.32914.874966.260722@grasshopper.cs.duke.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Fri, 28 Sep 2001 14:34:39 -0400 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG The cool thing I've always wanted to do with these programmable network adapters is to have them capture timestamps of when packets are received for high-accuracy latency measurements. The network adapter could drop a timestamp into some header when it's DMA'ed into the host's memory. The timestamp could come from some other PCI device (e.g., Datum bc635) which can provide a timestamp in 3 PCI bus cycles. The same sort of think could be done on transmit for suitably tagged packets. Some work I did a year or so ago measured the interrupt response time latency, and it was pretty impressive at how large and variable it could be. louie To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message