4 ms·

In case anyone else was wondering what "ability to control P-States and C-States" is about, I think this is a useful reference [1]. I guess with the C4-8Xlarge

by nissimk 12y ago

In case anyone else was wondering what "ability to control P-States and C-States" is about, I think this is a useful reference [1]. I guess with the C4-8Xlarge you control the entire physical machine and you can enable additional P-states to get more power out of the cpu while using more electricity. [1] http://www.xenserver.org/partners/developing-products-for-xenserver/19-dev-help/138-xs-dev-perf-turbo.html http://www.xenserver.org/partners/developing-products-for-xe...

tedunangst 12y ago
That's a strange feature to include on a machine I'm not paying the power or cooling bill for. Why would I ever set it to anything other than 11?
- dbarlett 12y ago
  From https://aws.amazon.com/blogs/aws/now-available-new-c4-instances/ https://aws.amazon.com/blogs/aws/now-available-new-c4-instan... : In some cases, your workload might not need all 18 of the cores (each of which runs two hyperthreads, for a total of 36 vCPUs on c4.8xlarge). To tune your application for better performance, you can manage the power consumption on a per-core basis. This is known as C-state management, and gives you control over the sleep level that a core may enter when idle. Let’s say that your code needs just two cores. Your operating system can set the other 16 cores to a state that draws little or no power, thereby creating some thermal headroom that will give the remaining cores an opportunity to Turbo Boost. You also have control over the desired performance (CPU clock frequency); this is known as P-state management. You should consider changing C-state settings to decrease CPU latency variability (cores in a sleep state consume less power, but deeper sleep states require longer to become active when needed) and consider changing P-state settings to adjust the variability in CPU frequency in order to best meet the needs of your application.
  - tedunangst 12y ago
    I question the real world utility/practicality of this, but thanks for the explanation. To elaborate: I start with (e.g.) a 2 cpu c4 instance. But my single thread performance isn't fast enough. So I'm going to spend a king's random to upgrade to a 36 cpu instance, just so I can disable 35 of those cpus? There are several other options I'd probably investigate first.
- idunno246 12y ago
  They'll raise the clock speed on a single core if it's cool enough iirc, so better single threaded performance
- bbgm 12y ago
  Some additional information on processor state control is available in the docs including some sample scenarioes http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/processor_state_control.html http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/processor...

by nissimk 12y ago

tedunangst 12y ago

That's a strange feature to include on a machine I'm not paying the power or cooling bill for. Why would I ever set it to anything other than 11?

dbarlett 12y ago
From https://aws.amazon.com/blogs/aws/now-available-new-c4-instances/ https://aws.amazon.com/blogs/aws/now-available-new-c4-instan... : In some cases, your workload might not need all 18 of the cores (each of which runs two hyperthreads, for a total of 36 vCPUs on c4.8xlarge). To tune your application for better performance, you can manage the power consumption on a per-core basis. This is known as C-state management, and gives you control over the sleep level that a core may enter when idle. Let’s say that your code needs just two cores. Your operating system can set the other 16 cores to a state that draws little or no power, thereby creating some thermal headroom that will give the remaining cores an opportunity to Turbo Boost. You also have control over the desired performance (CPU clock frequency); this is known as P-state management. You should consider changing C-state settings to decrease CPU latency variability (cores in a sleep state consume less power, but deeper sleep states require longer to become active when needed) and consider changing P-state settings to adjust the variability in CPU frequency in order to best meet the needs of your application.
- tedunangst 12y ago
  I question the real world utility/practicality of this, but thanks for the explanation. To elaborate: I start with (e.g.) a 2 cpu c4 instance. But my single thread performance isn't fast enough. So I'm going to spend a king's random to upgrade to a 36 cpu instance, just so I can disable 35 of those cpus? There are several other options I'd probably investigate first.
idunno246 12y ago
They'll raise the clock speed on a single core if it's cool enough iirc, so better single threaded performance
bbgm 12y ago
Some additional information on processor state control is available in the docs including some sample scenarioes http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/processor_state_control.html http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/processor...