Re: [patch 20/38] Minor fault path optimization.

Martin Schwidefsky
2007-05-02T10:44:46Z

On Sat, 2007-04-28 at 09:34 +0100, Christoph Hellwig wrote:
> Well, here's my powerpc patch to do the direct call that I sent out
> a few weeks ago. It not just speed up the pagefault path a lot,
> but also is a major code cleanup. Andi and Anton didn't like it
> because they have ambition for murky debugger code to possibly
> use it one day..

I thought about using a direct call for s390 as well. The advantage of a
direct call is that it avoids the overhead of a notifier call even if
kprobes is running. The disadvantage is that there cannot be a second
consumer of the fault notifications. I choose the middle way: avoid the
overhead if kprobes is not active and use the full notifier if kprobes
is running. It should not hurt the performance too badly since
kprobe_running is only true if the cpu gets a page fault while executing
a kprobe.