From 9c5320c8ea8b8423edca2c40cd559f1ce9496dab Mon Sep 17 00:00:00 2001 From: Jacob Shin Date: Thu, 4 Apr 2013 16:19:04 +0000 Subject: cpufreq: AMD "frequency sensitivity feedback" powersave bias for ondemand governor Future AMD processors, starting with Family 16h, can provide software with feedback on how the workload may respond to frequency change -- memory-bound workloads will not benefit from higher frequency, where as compute-bound workloads will. This patch enables this "frequency sensitivity feedback" to aid the ondemand governor to make better frequency change decisions by hooking into the powersave bias. Signed-off-by: Jacob Shin Acked-by: Thomas Renninger Acked-by: Borislav Petkov Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki --- Documentation/cpu-freq/governors.txt | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'Documentation') diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt index 4dfed30b7fd..66f9cc31068 100644 --- a/Documentation/cpu-freq/governors.txt +++ b/Documentation/cpu-freq/governors.txt @@ -167,6 +167,27 @@ of load evaluation and helping the CPU stay at its top speed when truly busy, rather than shifting back and forth in speed. This tunable has no effect on behavior at lower speeds/lower CPU loads. +powersave_bias: this parameter takes a value between 0 to 1000. It +defines the percentage (times 10) value of the target frequency that +will be shaved off of the target. For example, when set to 100 -- 10%, +when ondemand governor would have targeted 1000 MHz, it will target +1000 MHz - (10% of 1000 MHz) = 900 MHz instead. This is set to 0 +(disabled) by default. +When AMD frequency sensitivity powersave bias driver -- +drivers/cpufreq/amd_freq_sensitivity.c is loaded, this parameter +defines the workload frequency sensitivity threshold in which a lower +frequency is chosen instead of ondemand governor's original target. +The frequency sensitivity is a hardware reported (on AMD Family 16h +Processors and above) value between 0 to 100% that tells software how +the performance of the workload running on a CPU will change when +frequency changes. A workload with sensitivity of 0% (memory/IO-bound) +will not perform any better on higher core frequency, whereas a +workload with sensitivity of 100% (CPU-bound) will perform better +higher the frequency. When the driver is loaded, this is set to 400 +by default -- for CPUs running workloads with sensitivity value below +40%, a lower frequency is chosen. Unloading the driver or writing 0 +will disable this feature. + 2.5 Conservative ---------------- -- cgit v1.2.3-70-g09d2