On Wed, Jun 16, 2010 at 2:05 PM, Len Brown <lenb@xxxxxxxxxx> wrote: > Create /sys/power/policy_preference, giving user-space > the ability to express its preference for kernel based > power vs. performance decisions in a single place. > > This gives kernel sub-systems and drivers a central place > to discover this system-wide policy preference. > It also allows user-space to not have to be updated > every time a sub-system or driver adds a new power/perf knob. > This might be ok as a convince feature for userspace, but if that is the sole intention, is 5 states enough? Are these values sufficient? I can say at least for Android this will probably won't be as useful (but perhaps on your platforms it makes sense). As for a place for subsystems and drivers to check for what performance mode you're in, do my driver how to check two places now? Whats stopping someone from overriding cpufreq, or cpuidle? I might be confused here (if I am someone please correct me) but isn't this somewhat along he lines of pm runtime / pm qos if drivers want to check what power / performance state the system is in? -- Mike > policy_preference has 5 levels, from max_performance > through max_powersave. Here is how 4 parts of the kernel > might respond to those 5 levels: > > max_performance (unwilling to sacrifice any performance) > scheduler: default (optimized for performance) > cpuidle: disable all C-states except polling mode > ondemand: disable all P-states except max perf > msr_ia32_energy_perf_bias: 0 of 15 > > performance (care primarily about performance) > scheduler: default (optimized for performance) > cpuidle: enable all C-states subject to QOS > ondemand: all P-states, using no bias > msr_ia32_energy_perf_bias: 3 of 15 > > balanced (default) > scheduler: enable sched_mc_power_savings > cpuidle: enable all C-states subject to QOS > ondemand: all P-states, powersave_bias=5 > msr_ia32_energy_perf_bias: 7 of 15 > > powersave (can sacrifice measurable performance) > scheduler: enable sched_smt_power_savings > cpuidle: enable all C-states, subject to QOS > ondemand: disable turbo mode, powersave_bias=10 > msr_ia32_energy_perf_bias: 11 of 15 > > max_powersave (can sacrifice significant performance) > scheduler: enable sched_smt_power_savings > cpuidle: enable all C-states, subject to QOS > ondemand: min P-state (do not invoke T-states) > msr_ia32_energy_perf_bias: 15 of 15 > > Note that today Linux is typically operating in the mode > called "performance" above, rather than "balanced", > which is proposed to be the default. While a system > should work well if left in "balanced" mode, it is likely > that some users would want to use "powersave" when on > battery and perhaps shift to "performance" on A/C. > > Please let me know what you think. > > thanks, > Len Brown, Intel Open Source Technology Center > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
