2011/3/25 DM <dm(dot)aeqa(at)gmail(dot)com>:
> gettimeofday() on my new box is slow, after further research we found that,
> when we set ACPI=Off, we got a good clock performance even the explain
> analyze gave approximately gave the right values, but the hyperthreading is
> off.
Disabling ACPI also disables most CPU power management, so that
explains why you get a stable TSC that way. But that's not a real fix.
> could you guide me how to set, the parameter current_clocksource to TSC,
You can't "set" it, the kernel will automatically choose TSC, if it's
stable, at boot time; see messages in dmesg.
A better way to disable power management on CentOS is to disable the
'cpuspeed' service.
Note that this is not necessary for newer CPUs; Intel Nehalem and AMD
Phenom series have a stable TSC even with power management enabled.
Regards,
Marti