Re: pg9.0.3 explain analyze running very slow compared to a different box with much less configuration

2011/3/25 DM <dm.aeqa@gmail.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