Date: Tue, 9 May 2000 18:35:48 +0800 From: Tan Koan-Sin <freedom@csie.nctu.edu.tw> To: Theo PAGTZIS <T.Pagtzis@cs.ucl.ac.uk> Cc: freebsd-net@freebsd.org Subject: Re: Question on Tx queueing internals Message-ID: <20000509183548.A19208@ccserv.csie.nctu.edu.tw> In-Reply-To: <3917DF55.9ABD99AD@cs.ucl.ac.uk>; from T.Pagtzis@cs.ucl.ac.uk on Tue, May 09, 2000 at 10:50:14AM %2B0100 References: <3917DF55.9ABD99AD@cs.ucl.ac.uk>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, May 09, 2000 at 10:50:14AM +0100, Theo PAGTZIS wrote: > I am told that on the network card there is a Tx and Rx buffer.... > Is the output queue of an interface driver the same thing as a transmit > buffer on the actual network card or are they two different things...ie > when the ip_output passes the packet to the if_output function of the > Ether interface, the if_output will add the Ether header and then put it > on the output queue (if_snd). Is this output queue (the driver's output > queue ) the same as what one call the Tx/Rx buffer on the network card > or are is it a different one? They are different. The if_snd is a mbuf linked list in main memory. The Tx/Rx buffers are on the card. Take the Intel 82559 (fxp) on FreeBSD as a example, the Tx and Rx buffer on the network card are separate 3K FIFOs. > Also is the Tx buffer a different piece of memory than the Rx buffer on > the Ethernet card. I am asking that trying to understand whethe Tx and > Rx share a single buffer on the card so that Tx buffer could starv Rx > buffering... It depends the card you use. You must find the data sheet of the chips used on your card. -- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20000509183548.A19208>