Why is MySQL nearly twice as fast on Linux?

[Petri Helenius]

JG wrote:

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> I am just a layman here, but what does this mean?
>
You seem to have a very small number of active threads. When I tried 
supersmack on fairly old machine (800MHz dual pentium) I get ~30 active 
mysql threads using CPU between 1.5% and 3.5%.

I would suspect the test is limited by context switch and syscall 
overhead. With the old machine I see >70000 syscalls and >20000 context 
switches a second. So I suspect FreeBSD syscall overhead compared to 
linux must be higher. Mysql also asks for time repeatedly so make sure 
you are running ACPI timecounters. (don´t know if they are available on 
AMD64).

With the old machine I got 1360 qps for the select test. (although it´s 
not idle, but doing light other work)

Pete