https://bugzilla.kernel.org/show_bug.cgi?id=75121 Bug ID: 75121 Summary: Intel Pstate driver - powersave mode - CPU frequency too low Product: Power Management Version: 2.5 Kernel Version: 3.15rc3 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: cpufreq Assignee: cpufreq@xxxxxxxxxxxxxxx Reporter: dsmythies@xxxxxxxxx Regression: No Until recently, the difference between the intel_pstate driver in performance mode verses powersave mode was minimal to imperceptible. Now, the frequency response (meaning the rate of load / noload on a CPU) is drastically different than it used to be and often not even as good as the acpi-cpufreq driver in ondemand mode. This is a negative side effect from Commit fcb6a15c2e7e - intel_pstate: Take core C0 time into account for core busy calculation. I can revert to the same performance as previously for the intel_pstate driver in powersave mode by changing one line in the code (kernel = 3.15rc3-doug on the graphs). From this: sample->core_pct_busy = mul_fp(core_pct, c0_pct); to this: sample->core_pct_busy = core_pct; basically, reverting the commit. There has been other bug reports and threads: References: https://bugzilla.kernel.org/show_bug.cgi?id=70941 https://bugzilla.kernel.org/show_bug.cgi?id=66581 https://lkml.org/lkml/2014/2/19/626 In a moment, I will add 3 attachment graphs that detail the issue. -- You are receiving this mail because: You are the assignee for the bug. -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
