Before & After Under The Giant Lock

[Stephen Montgomery-Smith]

On Sun, 25 Nov 2007, Roman Divacky wrote:

> On Sun, Nov 25, 2007 at 02:41:35PM -0600, Stephen Montgomery-Smith wrote:
>>
>>
>> On Sun, 25 Nov 2007, Robert Watson wrote:
>>
>>> ........................
>>> In FreeBSD 8, I expect we'll see a continued focus on both locking
>>> granularity and improving opportunities for kernel parallelism by better
>>> distributing workloads over CPU pools.  This is important because the
>>> number of cores/chip is continuing to increase dramatically, so MP
>>> performance is going to be important to keep working on.  That said, the
>>> results to date have been extremely promising, and I anticipate that we
>>> will continue to find ways to better exploit multiprocessor hardware,
>>> especially in the network stack.
>>>
>>
>> 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.