Re: Scheduling Times --- Revisited

Paul Barton-Davis (pbd@Op.Net)
Tue, 29 Sep 1998 10:42:25 -0400

>Modify the driver's interrupt routine to get the data, put it in a buffer,
>and wake up a user level process when the buffer gets full, meanwhile
>switching to a new buffer. I don't mean to be condescending, but this
>is really basic producer/consumer type event gathering. Haven't you
>ever done this before? I just assumed that anyone who has done kernel
>performance work has had to gather event data from the kernel - how else
>would you do it without completely disturbing other system activity?

Well *I* don't mean to be condescending, but Larry, now you've blown
it for sure.

What Richard described *isn't* data GATHERING. Its data-based
manipulation of a device. You can't buffer the incoming data because
you need to use the incoming data and within 50us emit some new data
(based on the input) to the device. This isn't an example where you
can buffer up a certain amount of information, and then at the right
time do something with it.

Whether such a device is a good fit for a time-sharing OS is a
different question, but if it actually works the way Richard
describes, you're approach to controlling it will never work.

--pbd (who's written Unix drivers for similar drivers in the past)

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/