kernel-packages team mailing list archive

[Robert C Jennings <1477171@xxxxxxxxxxxxxxxxxx>]

Colin,

I read that you were considering[1] enabling it during t+1 and I wanted
your opinion for enabling it in Trusty on EC2 images at this time.
Also, what testing were you doing to evaluate this previously?  Thanks.

[1] https://lists.ubuntu.com/archives/kernel-team/2014-April/040795.html

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https://bugs.launchpad.net/bugs/1477171

Title:
  Enable intel_pstate by default on Trusty EC2 AMIs

Status in linux package in Ubuntu:
  New

Bug description:
  Please can the intel_pstate driver be enabled by default on the Ubuntu
  EC2 AMIs. On instances with support for C-states and P-States [1]
  there is a notable performance impact and lack of support for higher
  clock frequencies available due to the use of the acpi-cpufreq driver.
  For example on a c4.8xlarge the default frequency is limited to 2.9GHz
  when 3.2GHz is supported by the chip [2]. Some additional analysis is
  available here [3] and re-enabling it by default has been discussed
  [4] but this request is specifically for the EC2 AMIs.

  [1] http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/processor_state_control.html
  [2] http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/c4-instances.html
  [3] http://www.deplication.net/2015/07/c-states-and-p-states-with-ubuntu-1404.html
  [4] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1188647

  AMI: ami-47a23a30 (eu-west-1)

  $ lsb_release -d
  Description:    Ubuntu 14.04.2 LTS

  $ uname -a
  Linux ip-172-31-8-218 3.13.0-57-generic #95-Ubuntu SMP Fri Jun 19 09:28:15 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

  Default configuration (c4.8xl):
  $ sudo cpupower frequency-info
  analyzing CPU 0:
    driver: acpi-cpufreq
    CPUs which run at the same hardware frequency: 0
    CPUs which need to have their frequency coordinated by software: 0
    maximum transition latency: 10.0 us.
    hardware limits: 1.20 GHz - 2.90 GHz
    available frequency steps: 2.90 GHz, 2.90 GHz, 2.80 GHz, 2.70 GHz, 2.50 GHz, 2.40 GHz, 2.30 GHz, 2.20 GHz, 2.00 GHz, 1.90 GHz, 1.80 GHz, 1.70 GHz, 1.60 GHz, 1.40 GHz, 1.30 GHz, 1.20 GHz
    available cpufreq governors: conservative, ondemand, userspace, powersave, performance
    current policy: frequency should be within 1.20 GHz and 2.90 GHz.
                    The governor "ondemand" may decide which speed to use
                    within this range.
    current CPU frequency is 1.20 GHz (asserted by call to hardware).
    cpufreq stats: 2.90 GHz:70.40%, 2.90 GHz:0.00%, 2.80 GHz:0.00%, 2.70 GHz:0.00%, 2.50 GHz:0.00%, 2.40 GHz:0.00%, 2.30 GHz:0.00%, 2.20 GHz:0.00%, 2.00 GHz:0.00%, 1.90 GHz:0.00%, 1.80 GHz:0.00%, 1.70 GHz:0.00%, 1.60 GHz:0.09%, 1.40 GHz:0.00%, 1.30 GHz:0.00%, 1.20 GHz:29.51%  (5)
    boost state support:
      Supported: yes
      Active: yes

  With intel_pstate enabled (c4.8xl):
  $ sudo cpupower frequency-info
  analyzing CPU 0:
    driver: intel_pstate
    CPUs which run at the same hardware frequency: 0
    CPUs which need to have their frequency coordinated by software: 0
    maximum transition latency: 0.97 ms.
    hardware limits: 1.20 GHz - 3.50 GHz
    available cpufreq governors: performance, powersave
    current policy: frequency should be within 1.20 GHz and 3.50 GHz.
                    The governor "performance" may decide which speed to use
                    within this range.
    current CPU frequency is 3.20 GHz (asserted by call to hardware).
    boost state support:
      Supported: yes
      Active: yes

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