Re: serial.c (half duplex support)
Rogier Wolff (R.E.Wolff@BitWizard.nl)
Thu, 28 Oct 1999 15:24:34 +0200 (MEST)
tytso@mit.edu wrote:
> Date: Wed, 27 Oct 1999 17:00:37 +0200 (MEST)
> From: R.E.Wolff@BitWizard.nl (Rogier Wolff)
>
> Ok, let me clarify my point-of-view in this discussion:
>
> I'd expect Linux to get the most out of the hardware. In this case,
> transmissions achieving the full 115k2 on hardware that is capable of
> that.
> I'd -=like=- this to be achieved. If not, too bad. As long as it
> works.
>
> Well, let's see if we aren't not achieving that goal before we start
> getting our knickers in a twist. I did my original performance tuning
> and testing on an 40 MHz 386 with kermit transfers at 115kbps, and some
> of the games in the driver (like not touching the ISR register since on
> an 8 MHz ISA bus each I/O instruction really costs you) were done to get
> performance as high as possible.
>
> If we're having problems getting full 115k bps on hardware, especially
> on today's hardware (i.e. Pentiums with IDE DMA), I'd be a little bit
> surprised, quite frankly. But I'd really like to see some evidence that
> that's the case before we add all sorts of complexity to the serial driver.
Ted,
I have evidence of the interrupt routine not getting called for
extended periods, and in my case, it is clearly due to the IDE driver.
So as per your suggestion, lets get THAT darn thing fixed first. (But
I reiterate: It'd be nice if the serial driver would continue to work
perfectly even during such adverse conditions. Wishful thinking OK?)
My disk is capable of more than 5Mb per second, it doesn't do DMA
(it's on the blacklist), and pretend that I forget to do "hdparm -u
1", I see gaps in the interrupt routine calling of about 20ms.
I feel fine with gaps of about 1ms (transfer of 4k of data at 5Mb per
second), but I can't explain 20ms. Anybody know an explanation?
Roger.
--
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
"I didn't say it was your fault. I said I was going to blame it on you."
-
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/