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[Launchpad Bug Tracker <1477171@xxxxxxxxxxxxxxxxxx>]

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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

** Affects: linux-meta (Ubuntu)
     Importance: Undecided
         Status: New

-- 
Enable intel_pstate by default on Trusty EC2 AMIs
https://bugs.launchpad.net/bugs/1477171
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