Subject: Re: Warning to USB users
To: Lennart Augustsson <email@example.com>
From: Jason R Thorpe <firstname.lastname@example.org>
Date: 04/13/2001 10:57:43
On Fri, Apr 13, 2001 at 07:51:30PM +0200, Lennart Augustsson wrote:
> In a recent change Jason Thorpe turned on an option in the USB drivers
> that uses soft interrupts. If a port does not have generic soft interrupts (a
> prime example is i386) it instead uses a callout. In the latter case the
> interrupt latency increases greatly. For most USB devices this has no
> consequence, but if you are using, e.g., Ethernet adapters, the performance
> will be pretty bad (on my machine it went from 700 KB/s to 140 KB/s).
> If this worries you, just change sys/dev/usb/usb_port.h and comment
> out the define of USB_USE_SOFTINTR.
Unfortunately, SOFTINTR is going to be required due to another change
I'm going to make today.
I'll see about cooking up a generic soft interrupts implementation
for i386 today/tomorrow (I don't think I can wait for Bill Sommerfeld's
new MP-safe interrupt code to get finished).
-- Jason R. Thorpe <email@example.com>