* Peter Zijlstra <pet...@infradead.org> wrote:
> > Ah, I simply do not know what is cheaper, even on x86. Well,
> > we need to enable/disable irqs, but again I do not really
> > know how much does this cost.
>
> Ah good point about that IRQ thing, yes that's horribly
> expensive.
Enabling/disabling local IRQs is not really expensive (it's a
flat cost essentially - below 10 cycles on modern x86 CPUs) -
especially if we consider the 100x-1000x frequency difference
between schedule() and exit(), on typical systems:
$ grep -E 'ctxt|processes' /proc/stat
ctxt 47166536
processes 91876
And that's from a system that emphatically does not schedule
much. On others the difference is much larger.
So please don't push complexity into the scheduler from
lower-freq areas of the kernel!
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
