Re: context switch vs. signal delivery [was: Re: Accelerating user mode

Alan Cox (alan@redhat.com)
Sat, 3 Aug 2002 08:33:30 -0400 (EDT)


> actually the opposite is true, on a 2.2 GHz P4:
>
> $ ./lat_sig catch
> Signal handler overhead: 3.091 microseconds
>
> $ ./lat_ctx -s 0 2
> 2 0.90
>
> ie. *process to process* context switches are 3.4 times faster than signal
> delivery. Ie. we can switch to a helper thread and back, and still be
> faster than a *single* signal.

Thats interesting indeed. I'd not tried it with the O(1) scheduler.

> signals are in essence 'lightweight' threads created and destroyed for the
> purpose of a single asynchronous event, it's IMO a very inefficient and
> baroque concept for almost anything (but debugging and a number of very
> special uses). I'd guess that with a sane threading library a helper
> thread is faster for almost everything.

Which would argue UML ought to have a positively microkernel view of
syscalls - sending a message ?
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/