Re: Before & After Under The Giant Lock





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!

(Also when I run 4 threads with 2 cpus, each with hyperthreading, it goes 2.5 to 3 times faster - surprising since hyperthreading gets quite bad press for its performance improvements - I should add that Linux didn't do at all well at taking advantage of hyperthreading, running at the same speed as with 2 threads.)

Stephen

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