On 04/03/2015 11:08 AM, Linus Torvalds wrote:
> On Fri, Apr 3, 2015 at 9:54 AM, Denys Vlasenko <dvlas...@redhat.com> wrote:
>>
>> How about this version?
>> It's still isn't a star of readability,
>> but the structure of the 32-byte code block is more visible now...
>
> Do we really even want to be this clever in the first place?
>
> The thing is, when we take an interrupt:
>
> (a) the L1 I$ is always cold
>
> (b) the instruction decoder has never had time to run ahead
>
> (c) there are usually not that many different interrupts anyway, even
> under load (ie you'd have maybe disk and networking)
>
> (d) we intentionally spread out the different interrupt vector numbers
>
> (e) the 32-byte block thing is questionable, most older
> micro-architectures fetch in 16-byte blocks iirc.
>
For the record, I actually measured the impact of the jump-to-jump when
I wrote it. It has a small, *but measurable*, positive impact.
-hpa
--
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/
