In my previous post I’ve mentioned about the new HMC feature which can adjust CPU frequency. In this article I want to describe how to speed up the POWER system box, get more performance from the system. It is very easy to overclock the machine.
For POWER6, POWER7 MMB, MMC you need IBM Systems Director with Active Energy Manager plugin, but for MMD and POWER8 models you can do it directly from the ASM (Advanced System Management) or if you run the latest HMC code 8.8.2. there are two new commands chpwrmgmt and lspwrmgmt .
What is all about? IBM gave us an opportunity to modify a CPU frequency. Either to reduce consumed energy or overclock the CPU and boost the machine speed.
How to enable it in the ASM?
Open the ASM window from the HMC console. Expand the System Configuration > Power Management > Power Mode Setup.
In this screen you have four options.
- Disable Power Saver mode – this is default. No changes in the CPU frequency, resource will operate at 100% of nominal processor frequencies all time.
- Enable Static Power Saver mode – activates the Power Saver mode on IBM Power servers, fixing the processor frequency and voltage at a predetermined low-power mode. In another words, processor speed will be reduced in order to save energy if there is no demand for high CPU.
- Enable Dynamic Power Saver (favor power) mode – guarantees power savings by limiting the maximum frequency of the system under peak utilization under high utilization.
- Enable Dynamic Power Saver (favor performance) mode – allows a higher frequency range under
How to enable via CLI in the HMC?
To display current configuration type in the CLI
lspwrmgmt -m server_name -r sys
To change power management setting
chpwrmgmt -m server_name -r sys -o enable
chpwrmgmt -m server_name -r sys -o enable -t dynamic_favor_perf
but apparently the last command doesn’t work for me. It finishes with the error “HSCL02F2 The managed system does not support setting dynamic power saver modes from the management console”. I don’t why, well basically I don’t care because I can enable the same feature from the ASM.
Note that on multi-node systems such as the Power 770 or 780, each node’s processor frequency is
controlled independently. Across an entire system, processor core frequency will be maintained within
a 10% envelope.
So if you want to get max performance from your box, and you don’t care much about the electricity select Enable Dynamic Power Saver (favor performance) mode. You may achieve about +20% boost from the nominal speed.
What is the risk?
Well, I’m not a hardware engineer, but I believe it’s very safe. Changing Power Modes is an online operation, so you can give a try. But remember, if you have a system in maximum configuration and you will run overclocking, the power consumption will be higher than described in the hardware specification. So double check with your facility stuff that power cords are able to deliver that much energy.
Great thing about the overclock is that you get an extra performance (up to 20%) from the same system. You don’t have to buy anything (if you run MMD or Power8, otherwise you need IBM Systems Director and Active Energy plugin), you also don’t brake any licenses, and you get more performance. That’s why you probably will not hear about this feature from your sales-represantive;)
If you want to read more about it, check this IBM document.