Bruce Evans wrote:
> No, but the 3Com driver apparently is.  The sio driver wants to have
> fast interrupts.  It can't have them with the irq is shared, so its
> worst-case interrupt latency for a single serial port is increased
> from about 50 usec to many msec, depending other interrupt activity
> in the system (not limited to that for the shared irq except in some
> configurations).  Silo overflows occur at 115200 bps when the latency
> is more than about 1.5 msec.

Anyway to get the code to complain about the sharing of serial

Also, if there is a PCI interrupt for the serial (serial handled
by Northbridge... I'd like to see this, actually), shouldn't it
be capable of sharing *only* fast interrupts somehow?  It's an
obvious pessimization to mix other interrupts with fast interrupts,
but less obvious what would happen with fast + fast...

> FreeBSD on a 486/33 can handle about 40000 serial interrupts per second
> to do one character of i/o per interrupt).  Pessimizations in -current
> have only degraded this by a small factor (2?), provided the driver
> uses fast interrupts.  Lose another small factor (2?) for normal interrupts
> (using normal interrupts only loses a large factor for latency).

Any way to fix this, short of "don't run -current"??

-- Terry

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