Good CPU but very high low load

Wils_Gomes

Hi, I have the following CPUs: Intel(R) Core(TM) i3-3220 CPU @ 3.30GHz But running the cpu test I get the following numbers: Compiled with: 4.1.2 20080704 (Red Hat 4.1.2-52) Expected time on Core 2, 2.53GHz: ~9.5s Expected time on Nehalem, 2.67GHz: ~9.0s Expected time on Xeon 5670, 2.93GHz: ~8.0s This machine's time: CPU Time: 7.550000s <<<< good Real Time:7.550000s <<<< good Some machines automatically throttle the CPU to save power. This test can be done in <100 microseconds (60-70 on Xeon 5670, 2.93GHz). Low load times much larger than 100-200us or much larger than the corresponding high load time indicate low-load throttling, which can adversely affect small query / concurrent performance. This machine's high load time: 64 microseconds. This machine's low load time: 212 microseconds. <<<< bad Please, how can I change the CPU settings to reach no more than 114 microseconds in low load? thank you

Daniel_Leybovic

Hi! Good question about system administration. You can control CPU frequency with CPU Governor, but Vertica recommends to disable CPU frequency scaling: https://my.vertica.com/docs/6.1.x/HTML/index.htm#18481.htm I will give a couple links for reading, also Internet is full in other wonderful articles almost for all distributions, just search "Linux CPU Governor" 1. https://www.kernel.org/doc/Documentation/cpu-freq/governors.txt 2. https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Power_Management_Guide/cpufreq_governors.html 3. http://www.thinkwiki.org/wiki/How_to_make_use_of_Dynamic_Frequency_Scaling

Wils_Gomes

Ops, is missing the rest of the post =P This machine's high load time: 64 microseconds. This machine's low load time: 208 microseconds. <--- bad

Wils_Gomes

Daniel, thank you for for the "Linux CPU Governor" links, by the way I have read the Vertica docs before my posting and did disable the " Enhanced Intel SpeedStep Technology" in BIOS but I am still getting those huge difference between low/high load times =(

[Deleted User]

For what it's worth, we have seen occasional issues/bugs with brand-new processors on older motherboards, where the BIOS setting doesn't fully disable some new CPU-scaling features of the new processor. If that's the case, you'd have to speak with your hardware vendor. (Also, you could try disabling other power-management-related BIOS settings, if you have any. Different BIOSes have different names for things, and new CPU-scaling technologies come out on a regular basis.) Daniel's references on CPU governors are also a good place to look / play around with.