Problem with c-states on intel cpu, max turbo frequency can not be reached with intel idle driver

Solution Verified - Updated -

Issue

  • Problem with c-states on intel cpu, max turbo frequency can not be not reached with intel idle driver
  • max turbo frequency can not be not reached with intel idle driver
  • On our very new system with running Red Hat 6.4 we see that the maximum possible turbo frequency of 3500 MHz with one core active is not achieved. Instead only 3000 MHz which is the maximum when all cores are active is reported. The reason for this is that the inactive cores are not put to deeper C-states than C1. Preventing the kernel from overriding the BIOS C-states via adding intel_idle.max_cstate=0 now the system achieves 3500 MHz with one core active as expected.
    So the Intel Idle driver seems to be running not correctly.

Environment

  • Red Hat Enterprise Linux (RHEL) 6
  • Red Hat Enterprise Linux OpenStack Platform (RHELOSP) 5
  • kernel <2.6.32-358.11.1.el6
  • very new Intel cpu/chipset, as of June 2013

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