drm/vmwgfx: Fix compat shader namespace
Dan Carpenter
dan.carpenter at oracle.com
Thu Jul 10 02:33:18 PDT 2014
On Wed, Jul 09, 2014 at 11:31:45PM +0200, Thomas Hellström wrote:
> >Speaking of verbose, all the likely/unlikely annotations should be
> >removed.
>
> Is this your personal opinion or has there been some kind of kernel
> developer agreement not to add this annotation and remove it from
> the kernel tree? If not, I prefer to keep it.
It obviously makes the code less readable. It makes a small speedup if
the code is called 10000 times with the and the expected value is true
every time. If more than 1 out of 10000 values is unexpected then it is
a slow down.
There are two rules of thumb for likely/unlikely:
1) Don't use it in the drivers/ directory.
2) Or don't use it without benchmarking it.
These are general rules, not mine.
In the olden days we used to use it more often but then people did
benchmarking and likely/unlikely annotations didn't make a single
measurable difference on normal benchmarks at all. Maybe on a micro
benchmark. Also perhaps in those days people hadn't done branch
profiling so we were getting a lot of unexpected conditions and the slow
downs were canceling the speed ups.
regards,
dan carpenter
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