Accurate/Fine-grained timing of latency in atheros drivers

From: Sam Pierson (samuel.pierson_at_gmail.com)
Date: 06/27/05

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    Date: Mon, 27 Jun 2005 16:17:34 -0500
To: FreeBSD Hackers <freebsd-hackers@freebsd.org>

    Hey guys,

    In a current project, I need to find out exactly how long it takes to send
    a 802.11 packet and how much time is spent in the following stages:

    send time - time spent constructing message, including context switches
    and other delays and the time it takes to transfer the message to the
    network card.

    access time - delay which we experience waiting to access the transmitting
    channel. Normally this would include the RTS and CTS queuing signals,
    but for this application, I have to disable them. Is it possible that no time
    is spent waiting here, if I have disabled the whole CSMA scheme on the
    hardware level?

    propagation time - how long it takes to get to the receiver, once it has left
    our card

    receive time - how long it takes for the receiving network card to get the
    message and notify the host that it has something to read.

    Am I going to have to put in hardware interrupts to time these events or
    are such tools already available?

    -Sam
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