Before & After Under The Giant Lock

[Stephen Montgomery-Smith]

On Sun, 25 Nov 2007, Kip Macy wrote:

>>>>
>>>> I just want to add my 2 cents, that my recent experience with FreeBSD MP
>>>> has been extremely positive.  I tend to use highly CPU bound MP programs,
>>>> typically lots and lots of floating point operations.  It used to be that
>>>> Linux beat FreeBSD hands down - now FreeBSD seems to have a slight edge!
>>>> Basically my program runs about twice as fast when I run two threads as
>>>> opposed to one - I cannot see doing any better than that!
>>>
>>> pure computation does not need kernel operations most of the time.. ie.
>>> multi-threading kernel wont help much ;)
>>>
>>
>> Yes, I know.  But something else was also done to FreeBSD, perhaps fine
>> tuning with the scheduler, that did bring about massive improvements.
>>
>
> I assume you're using ULE. Jeff has gone to great lengths to take
> cache affinity into account. This may be what you are benefiting from.

No, I'm using 4BSD under FreeBSD 7.0.  But I just tried it with ULE under 
FreeBSD 8.0 (Witnesses and invariants switched off), and the speed 
marginally slower, but only by 2% or so.