On Mon, Mar 27, 2017 at 09:58:17AM -0700, Matthew Wilcox wrote: > On Mon, Mar 27, 2017 at 05:15:00PM +0200, Jesper Dangaard Brouer wrote: > > And I also verified it worked: > > > > 0.63 │ mov __preempt_count,%eax > > │ free_hot_cold_page(): > > 1.25 │ test $0x1f0000,%eax > > │ ↓ jne 1e4 > > > > And this simplification also made the compiler change this into a > > unlikely branch, which is a micro-optimization (that I will leave up to > > the compiler). > > Excellent! That said, I think we should define in_irq_or_nmi() in > preempt.h, rather than hiding it in the memory allocator. And since we're > doing that, we might as well make it look like the other definitions: > > diff --git a/include/linux/preempt.h b/include/linux/preempt.h > index 7eeceac52dea..af98c29abd9d 100644 > --- a/include/linux/preempt.h > +++ b/include/linux/preempt.h > @@ -81,6 +81,7 @@ > #define in_interrupt() (irq_count()) > #define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) > #define in_nmi() (preempt_count() & NMI_MASK) > +#define in_irq_or_nmi() (preempt_count() & (HARDIRQ_MASK | > NMI_MASK)) > #define in_task() (!(preempt_count() & \ > (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) >
No, that's horrible. Also, wth is this about? A memory allocator that needs in_nmi()? That sounds beyond broken.
