Re: Before & After Under The Giant Lock



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.
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