Public bug reported: [ 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+re4efyzjs12o...@mail.gmail.com/) * Patch for Meteor Lake: https://lore.kernel.org/lkml/cajz5v0i8rnws9ogxxqvocg4rhhn7x3elcrupogrs1ip8hns...@mail.gmail.com/ * Patch for Arrow Lake: https://lore.kernel.org/lkml/CAJZ5v0g+R6JK=T9EjmweRPKmcorw93JmPM4u-Z=pywv6kh7...@mail.gmail.com/ (both merged in 6.11-rc1 https://lore.kernel.org/lkml/cajz5v0h7ohr7ipj6ubgtlez238jzktshh93cye_gdx5j+zb...@mail.gmail.com/) ** Affects: linux (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2077470 Title: [SRU][Noble] Bad EPP defaults cause performance regressions on select Intel CPUs To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2077470/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
