Why is MySQL nearly twice as fast on Linux?

[JG]

At 08:09 PM 5/23/2004 +0300, you wrote:
>JG wrote:
>
>>
>>
>>
>>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%.

You mean where I have the 3 instances of mysqld running in top?  You have 
~30 instances?

Why would your box use more? Is there any configuration or flag in mysql 
that would cause this?

How was your mysql compiled? What version of FreeBSD are you running?

>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).

I know that this FreeBSD/AMD64 reports that it is using ACPI... how do I 
find out if its using timecounters, or using them properly?

FWIW...

amd64f# cat /var/log/dmesg.today | grep ACPI
ACPI APIC Table: <A M I  OEMAPIC >
Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
cpu0: <ACPI CPU> on acpi0
pcib0: <ACPI Host-PCI bridge> port 0xcf8-0xcff on acpi0
pci0: <ACPI PCI bus> on pcib0
pcib1: <ACPI PCI-PCI bridge> at device 6.0 on pci0
pci3: <ACPI PCI bus> on pcib1
pcib2: <ACPI PCI-PCI bridge> at device 10.0 on pci0
pci2: <ACPI PCI bus> on pcib2
pcib3: <ACPI PCI-PCI bridge> at device 11.0 on pci0
pci1: <ACPI PCI bus> on pcib3