Public bug reported: The intel pstate driver is currently quite broken on on Skylake hardware.
The symptom is that the pstate driver can scale the frequency up, but wont then scale it back down. So as soon as you hit a decent amount of CPU load, you get stuck fluctuating in the turbo frequency ranges, never even dropping as low as the base clock frequency. Obviously this has very negative consequences for battery life. Commit 74da56ce5c6715630aed3ccc0fcb86a9210c1a56 fixes this upstream, which is included in 4.3rc2: https://git.kernel.org/cgit/linux/kernel/git/next/linux- next.git/commit/?id=74da56ce5c6715630aed3ccc0fcb86a9210c1a56 I built a custom Ubuntu kernel with this commit and tested it on a laptop with a Skylake i7-6700 CPU. As measured by powerstat, this commit dropped the idle power consumption by 11 watts (from 34 to 23 watts, screen backlight was off during the test). I also tested this custom kernel on Haswell and Ivy Bridge hardware to make sure it didn't introduce any behaviour changes in the pstate driver on older hardware. As far as I can tell, on this older hardware pstate is behaving exactly the same with and without this commit. Thanks! ** Affects: linux (Ubuntu) Importance: Undecided Status: New ** Tags: skylake wily ** Attachment added: "intel_pstate-fix-PCT_TO_HWP-macro.patch" https://bugs.launchpad.net/bugs/1499040/+attachment/4472580/+files/intel_pstate-fix-PCT_TO_HWP-macro.patch -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1499040 Title: Wily: Skylake: intel_pstate: fix PCT_TO_HWP macro Status in linux package in Ubuntu: New Bug description: The intel pstate driver is currently quite broken on on Skylake hardware. The symptom is that the pstate driver can scale the frequency up, but wont then scale it back down. So as soon as you hit a decent amount of CPU load, you get stuck fluctuating in the turbo frequency ranges, never even dropping as low as the base clock frequency. Obviously this has very negative consequences for battery life. Commit 74da56ce5c6715630aed3ccc0fcb86a9210c1a56 fixes this upstream, which is included in 4.3rc2: https://git.kernel.org/cgit/linux/kernel/git/next/linux- next.git/commit/?id=74da56ce5c6715630aed3ccc0fcb86a9210c1a56 I built a custom Ubuntu kernel with this commit and tested it on a laptop with a Skylake i7-6700 CPU. As measured by powerstat, this commit dropped the idle power consumption by 11 watts (from 34 to 23 watts, screen backlight was off during the test). I also tested this custom kernel on Haswell and Ivy Bridge hardware to make sure it didn't introduce any behaviour changes in the pstate driver on older hardware. As far as I can tell, on this older hardware pstate is behaving exactly the same with and without this commit. Thanks! To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1499040/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
