Re: latest 'guaranteed low latency' patch against 2.2.14

From: John Regehr (jdr8d@cs.virginia.edu)
Date: Wed Feb 09 2000 - 11:21:38 EST


> how do you improve task-execution latency without rescheduling actually?
> Short of adding new hardware, or without adding a new (limited) API to
> execute user-specified code. Ie. how do you reschedule to a generic
> user-task without actually rescheduling?

Well, in NT, IRIX, BeOS, and (I think) Solaris tasks running in kernel
mode can be preempted any time as long as they're not holding a spinlock.

Certainly making a kernel preemptible increases complexity. I'd be
interested in hearing about the tradeoffs here - hasn't Larry McVoy talked
about this in the past on this list?

> any device interrupt can be turned into an NMI interrupt - of course
> special handlers have to be written, and careful coding is needed as no
> other kernel facilities can be relied on.

Won't this hose RT-Linux? If random device drivers start using NMI (as
Alan Cox suggested in a different mail) then it would be really nice if
there was a way to disable this behavior at compile time.

John Regehr

-
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/



This archive was generated by hypermail 2b29 : Tue Feb 15 2000 - 21:00:15 EST