Re: [Discuss-gnuradio] Volk branch on github

[Josh Blum]

On 02/16/2012 11:24 AM, Tom Rondeau wrote:
> On Thu, Feb 16, 2012 at 2:08 PM, Josh Blum <address@hidden> wrote:
> 
>>
>>> Also, you never want to work on the smallest amount of memory possible.
>>> This is covered in my discussion on my blog. Making arbitrarily small
>> calls
>>> to work functions causes much more overhead than just running the
>> unaligned
>>> version of a Volk call. I found this out pretty quickly when I started
>>> looking into things. Better to process a large chunk to get back into
>>> alignment than try to handle calls to small amounts of data.
>>>
>>
>> Perhaps this is because you have a processor that doesn't penalize you
>> for unaligned loads/stores.
>>
>> -Josh
>>
> 
> I tested this on a handful of different processors: Core2Due, QuadCore, i7
> (first get), i7 (second gen) and they all told me the same thing. You are

For most if not all recent x86 processors there is no unaligned penalty.
You should be able to always call the unaligned volk routine and see no
difference in performance. I'm wondering about neon for example, which
has a penalty. And I suppose to a lesser extent, older x86 processors. I
dont have numbers now, but I think the volk profiler can confirm this
about said processors.

-Josh