mysql scaling questions

[Kris Kennaway]

Josh Carroll wrote:
>> Does anyone have a theory why syscalls are so expensive in FreeBSD? Here
>> are the results of unixbench 4.1 on two machines. First is the machine
>> running FreeBSD HEAD (debugging disabled) on a dual-core Athlon 64 (i386
>> mode), 2 GHz:
> 
> I ran the syscall benchmark from UnixBench on the same hardware (Intel
> Q6600 @ 3.2 GHz) for both FreeBSD 7.0-RC1 (amd64) and Knoppix 5.1
> (Linux 2.6.9 PREEMPT kernel, i386).
> 
> Per the comments in this thread, i386 syscalls should be less
> expensive than amd64 syscalls, so the results are interesting:
> 
> FreeBSD 7.0-RC1 (amd64):  System Call Overhead
> 15000.0  1103233.7      735.5
> Knoppix Linux 2.6.9 (i686):   System Call Overhead
>     15000.0  1108869.7      739.2
> 
> I can try to find a Linux live CD with a 2.6.x x86-64 kernel for a
> valid apples-to-apples comparison, but thought these results might
> provide some parity/insight.
> 
> Doesn't look like the syscalls are slower at all on FreeBSD.
> 
> Josh
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> 
> 

Per later discussion you will also need to either comment out the 
syscalls that are (might be) being cached by glibc to artificially 
inflate its reported rate, or verify that it is not doing so.

Kris