Re: Inquiry: Should we remove "isolcpus= kernel boot option? (may have realtime uses)

From: Ingo Oeser
Date: Mon Jun 02 2008 - 19:56:23 EST


Hi Max,
Hi Peter,

On Tuesday 03 June 2008, Max Krasnyansky wrote:
> Ingo, I just wanted to elaborate on what Peter is saying. That CPU will still
> have to be _booted_ properly. It may be used for hard- and soft- interrupt
> processing, workqueues (internal kernel queuing mechanism) and kernel timers.

Oh! Didn't know that user process scheduling is so much
> In your particular case you're much much much better off with doing
> echo 0 > /sys/devices/system/cpuN/online
> either during initrd stage or as a first init script.
> That way bad cpu will be _completely_ disabled.

The initrd is from the distribution. I have no sane way to change it
fast and permanent. Can I change the initrd and still have a certified
RHEL or SLES? Are there initrd hooks, which survive packet installation?

I would really appreciate some way to keep the kernel from using
a CPU at all to do fault isolation. If possible not even booting it.

Bootparameters survived all distro fiddling so far. I love them!

Try to convince a hardware vendor, that you don't have a software bug.
Try to convince him that you didn't break the hardware by swapping it around.

So I'll ACK removing isolcpus, if we get a better replacement boot option.


Best Regards

Ingo Oeser
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/