On Sat, 1 May 1999, Paul Jakma wrote:
> ah ok, so the kernel only ran on one CPU, but processes could run on
> both. i had thought that this was due to a global kernel lock, not
> interrupts.. by what mechanism can the kernel on cpu#0 schedule a
> task to run on cpu#1?
>
> Hopefully widely available K7 SMP systems will accelerate development
> of EV6 SMP and help the 21264 out aswell.
no.. You misunderstand.
In unix the kernel runs in process context..
that i knew. so a process can trap to kernel mode via a syscall on
cpu1 and hence the kernel runs on that cpu. i grok that.
So the kernel ran on both cpus, but two copies of the kernel
could not run at one (except when doing some trivial things). All
the int's were processes by cpu0.
afaik, the scheduler is called by the timer interrupt, right? so if
the timer int is only delivered to cpu0, how can a scheduler hand
over control to a process to run on cpu1, when the scheduler can't
run on cpu1.
i'd be glad if you could fill me in on what i'm missing.
regards,
-- Paul Jakma paul@clubi.ie http://hibernia.clubi.ie PGP5 key: http://www.clubi.ie/jakma/publickey.txt ------------------------------------------- Fortune: Systems programmers are the high priests of a low cult. -- R.S. Barton
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