On Mon, 26 Feb 2007, Benjamin LaHaise wrote:
>
> Side note: this patch adds several function calls (4), several additional
> L1 cache touches and a generally inefficient code path to *every single
> interrupt that exits from the idle poll*, not to mention the extra (useless,
> as it doesn't get used on 99.9% of deployed systems) function call and cache
> touches to every single interrupt.
It is in fact possible that the floppy failure might just be from some
timing-dependent thing, and the slowdown itself is the problem.
Although I do find that a bit unlikely, since machines these days are
about a million times faster than they used to be, so even if it's
unnecessarily slow, it shouldn't be noticeable for a floppy drive.
> Keep in mind that systems acting as routers will often be sitting in
> the idle loop when processing interrupts. At the very least this
> overhead (which is noticable on profiles) should be configurable. I
> don't think that my 586 class embedded routers really need this crap to
> be going into the kernel.
I'm inclined to agree. Considering that the patch is known to cause
problems, and that it's apparently broken on x86 *anyway* (the
idle_notifier_register function isn't even exported), and considering that
it's clearly bad for interrupt performance and could have been done a lot
better, I would suggest just ripping it all out.
And I think we should do the same for x86-64 too..
Linus
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