[SRU][N][PATCH v3 0/6] Update default Intel EPP Values

[Pedro Henrique Kopper]

BugLink: https://bugs.launchpad.net/bugs/2077470

SRU Justification:

[ Impact ]

 * Intel currently provides an Energy Performance Preference (EPP) tunable via its intel_pstate
   to control power management. It ranges from 0 (performance) to 255 (powersaving).
 * When the governor is set to powersave, which is the default, the EPP value of balance_performance
   controls how the CPU frequency scaling occurs. However, on some platforms (Emerald Rapids, Meteor
   Lake, Arrow Lake) it is set to a very conservative value out of the box, resulting in degraded
   performance by default.
 * These EPP tuning values work as a black-box and vary per-generation, so having the latest values
   available is important to keep systems running at maximum achievable performance. Both Intel and
   Canonical perform this kinds of tests and supply values.

[ Test Plan ]

 * Perform a benchmark on a stock Ubuntu 24.04 image

 * On Emerald Rapids:
 * Change the EPP to 32 by executing
   echo 32 | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference

 * Observe the performance difference. In our internal testing, we found the following results
   when setting EPP to 32:
   POV-Ray: 32% faster | 12% less energy
   OpenSSL: 12% faster | energy within 1%
   Build Linux Kernel: 29% faster | 18% less energy

 * On Meteor Lake and Arrow Lake:
 * Change the EPP to 64 by executing
   echo 64 | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference

 * Observe the performance difference. Intel found out the following for Meteor Lake:
 > Speedometer 2.1
 > score: +19%
 > Perf/watt: +5.25%
 >
 > Webxprt 4 score
 > score: +12%
 > Perf/watt: +6.12%
 >
 > 3DMark Wildlife extreme unlimited score
 > score: +3.2%
 > Perf/watt: +11.5%
 >
 > Geekbench6 MT
 > score: +2.14%
 > Perf/watt: +0.32%
 >
 > Also update balance_power EPP default to 179. With this change:
 > Video Playback power is reduced by 52%
 > Team video conference power is reduced by 35%
 * The same outcome should be obtained from Arrow Lake as per Intel.

[ Where problems could occur ]

 * The regression risks are very low. The CPU should perform in a more efficient zone, resulting in
   overall power savings, despite the more aggressive scaling. This was verified using a Yokogawa WT310
   power meter and an Emerald Rapids reference platform.
 * Tests on Meteor Lake and Arrow Lake were performed by Intel. They were not independently verified by
   Canonical.

[ Other Info ]

 * Patch for Emerald Rapids: https://lore.kernel.org/lkml/Zqu6zjVMoiXwROBI@capivara/ (merged in 6.11-rc3 https://lore.kernel.org/lkml/CAJZ5v0hQ3O7E3ygvFKbzjkJbx7pddyD9Qc+rE4EFYzJS12oTMg@mail.gmail.com/)
 * Patch for Meteor Lake: https://lore.kernel.org/lkml/CAJZ5v0i8RnWs9OgxxqVOCG4RHhN7X3ELcruPoGrS1iP8hNSGsw@mail.gmail.com/ 
 * Patch for Arrow Lake: https://lore.kernel.org/lkml/CAJZ5v0g+R6JK=T9EjmweRPKmcorw93JmPM4u-Z=pywv6kH7zUA@mail.gmail.com/ (both values for MTL and ARL merged in 6.11-rc1 https://lore.kernel.org/lkml/CAJZ5v0h7OHR7ipj6ubgTLEz238JZkTshh93CYe_gDx5j+zBwfA@mail.gmail.com/)


Pedro Henrique Kopper (1):
  cpufreq: intel_pstate: Update Balance performance EPP for Emerald
    Rapids

Srinivas Pandruvada (4):
  cpufreq: intel_pstate: Allow model specific EPPs
  cpufreq: intel_pstate: Update default EPPs for Meteor Lake
  cpufreq: intel_pstate: Update Meteor Lake EPPs
  cpufreq: intel_pstate: Use Meteor Lake EPPs for Arrow Lake

Tony Luck (1):
  cpufreq: intel_pstate: Switch to new Intel CPU model defines

 drivers/cpufreq/intel_pstate.c | 128 ++++++++++++++++++++-------------
 1 file changed, 80 insertions(+), 48 deletions(-)

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2.43.0