Re: Can context switches be faster?

[Jeremy Fitzhardinge]

John Richard Moser wrote:
> That's a load more descriptive :D
>
> 0.890 uS, 0.556uS/cycle, that's barely 2 cycles you know.  (Pentium M)
> PPC performs similarly, 1 cycle should be about 1uS.
>   

No, you're a factor of 1000 off - these numbers show the context switch 
is around 1600-75000 cycles.  And that doesn't really tell the whole 
story: if caches/TLB get flushed on context switch, then the newly 
switched-to task will bear the cost of having cold caches, which isn't 
visible in the raw context switch time.

But modern x86 processors have a very quick context switch time, and I 
don't think there's much room for improvement aside from 
micro-optimisations (though that might change if the architecture grows 
a way to avoid flushing the TLB on switch).

   J
-
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/