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

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If it's a HP box you can also turn this off via the bios via your RBSU:

Starting with HP ProLiant G6 servers that utilize Intel Xeon processors, setting the HP Power Profile 
Option in RBSU to Maximum Performance Mode sets these recommended additional low-latency options 
for minimum BIOS latenc


-----Original Message-----
From: pgsql-performance-owner@xxxxxxxxxxxxxx [mailto:pgsql-performance-owner@xxxxxxxxxxxxxx] On Behalf Of Marti Raudsepp
Sent: Friday, March 25, 2011 3:30 AM
To: DM
Cc: Achilleas Mantzios; pgsql-performance@xxxxxxxxxxxxxx
Subject: Re:  pg9.0.3 explain analyze running very slow compared to a different box with much less configuration

2011/3/25 DM <dm.aeqa@xxxxxxxxx>:
> gettimeofday()Âon 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

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