Hi, > On 23 Jul 2015, at 02:22, Sepherosa Ziehau <sepher...@gmail.com> wrote: > > First of all, I'd like to introduce the major power management > stuffs currently available on DragonFly. > > - ACPI P-state. It has the proper CPU power domain support. > - ACPI C-state. Unlike other BSDs, on relatively recent Intel CPUs > (the oldest Intel CPU I tested is Sandy Bridge), we don't use I/O > port to enter ACPI C2/C3, instead, we give hint to BIOS that 'native > C2/C3' is supported. BIOS will send us ACPI C2/C3 to mwait C-states > maps through GAS.
Have you checked why other BSDs don’t do that? Broken BIOSs are all too common. > And the GAS will also contain information about > whether checking bus master status is needed or not for ACPI C3. > Given most of recent Intel CPUs (since core2) do not require bus > master arbitration or flush cache before entering ACPI C3, entering > APIC C-state becomes simple monitor/mwait instructions. > - Intel Performance and Energy Bias Hint. According to Intel software > developer manual, it's a "hint to guide the hardware heuristic of > power management features to favor increasing dynamic performance or > conserve energy consumption". > - Mwait C-state. This requires mwait extension, which is available on > almost all of the recent CPUs. If we need to check bus master > status, flush cache or bus master arbitration before entering ACPI > C3, then mwait C-states deeper then C2/0 will not be used. > > ======================== > > ACPI P-state > > On Intel i7-3770 3.40GHz and Intel i5-3230M 2.60GHz and many other > recent Intel CPUs (tested by dillon@), adjusting ACPI P-state does > _not_ reduce power consumption at all. On these CPUs, adjusting ACPI > P-state only affects how dynamic frequency works, e.g. on Intel > i5-3230M (system is idle): > ACPI P-state 2601 (TurboBoost): > hw.sensors.cpu0.freq0: 2721627000 Hz (cpu0 freq) > hw.sensors.cpu1.freq0: 2751159000 Hz (cpu1 freq) > hw.sensors.cpu2.freq0: 2627060000 Hz (cpu2 freq) > hw.sensors.cpu3.freq0: 2191103000 Hz (cpu3 freq) > ACPI P-state 2600: > hw.sensors.cpu0.freq0: 2266678000 Hz (cpu0 freq) > hw.sensors.cpu1.freq0: 2401977000 Hz (cpu1 freq) > hw.sensors.cpu2.freq0: 2248562000 Hz (cpu2 freq) > hw.sensors.cpu3.freq0: 2406333000 Hz (cpu3 freq) > ACPI P-state 1200: > hw.sensors.cpu0.freq0: 1197281000 Hz (cpu0 freq) > hw.sensors.cpu1.freq0: 1197340000 Hz (cpu1 freq) > hw.sensors.cpu2.freq0: 1197284000 Hz (cpu2 freq) > hw.sensors.cpu3.freq0: 1197300000 Hz (cpu3 freq) > > On Intel E5-2620 v2 2.10GHz, adjusting ACPI P-state reduces power > consumption. However, as far as I tested, the power consumption > change is only between TurboBoost ACPI P-state and non-TurboBoost > ACPI P-state, e.g. on Intel E5-2620 v2 (2-way): > ACPI P-state 2101 (TurboBoost): 94.6w > ACPI P-state 2100: 92.5w > ACPI P-state 1200: 92.5w > > ======================== > > Intel Performance and Energy Bias Hint > > To be frank, I didn't notice power consumpion or thermal changes by > adjusting this hint on any of the Intel CPUs that I tested. > > ======================== > > ACPI C-state > > Since on all of the Intel CPUs I tested ACPI C-states are mapped to > mwait C-states and do not require bus master operations; we move on > to mwait C-states. > > ======================== > > Mwait C-state > > It seems to be the only power management stuff that reduces power > consumption on all Intel CPUs dillon@ and I tested. The power > consumption on the CPUs I tested. > > Intel i7-3770 (ACPI P-state 3401): > mwait C1/0: 38.3w > mwait C1/1: 38.3w > mwait C2/0: 37.6w > mwait C3/0: 36.8w > > Intel i5-3230M (ACPI P-state 2601): > mwait C1/0: 14.7w > mwait C1/1: 14.7w > mwait C2/0: 13.3w > mwait C3/0: 12.9w > mwait C4/0: 12.9w > mwait C4/1: 12.9w > > Intel E5-2620 v2 (2-way) > (ACPI P-state 2101 TurboBoost): > mwait C1/0: 94.6w > mwait C1/1: 94.6w > mwait C2/0: 93.7w > mwait C3/0: 92.3w > (ACPI P-state 2100~1200): > mwait C1/0: 92.5w > mwait C1/1: 92.5w > mwait C2/0: 85.3w > mwait C3/0: 83.8w > > One thing in common is that there is no power consumption difference > between mwait C1/0 (C1) and C1/1 (C1E?); probably because C1E will be > entered once all cores are in C1 state, as mentioned in Intel E5-2600 > v2 datasheet. > > Though deep mwait C-states reduce power consumption, you will have to > pay for the additional latency. The latency could be as high as 40us > if the CPU enters deep package C-state. The average latency I > gathered on various types of CPUs I tested (by using > debug.ipiq.latency_test): > > Intel i7-3770 (ACPI P-state 3401): > mwait C1/0 and C1/1: 760ns > mwait C2/0: 18us > mwait C3/0: 25us > > Intel i5-3230M (ACPI P-state 2601): > mwait C1/0 and C1/1: 950ns > mwait C2/0: 21us > mwait C3/0, C4/0, C4/1: 26us > > Intel E5-2620 v2 (2-way) > (ACPI P-state 2101 TurboBoost) > mwait C1/0 and C1/1: same package 2200ns, different package 2600ns > mwait C2/0: same package 15us, different package 24us > mwait C3/0: same package 33us, different package 37us > (ACPI P-state 2100) > mwait C1/0 and C1/1: same package 2200ns, different package 2600ns > mwait C2/0: same package 15us, different package 22us > mwait C3/0: same package 26us, different package 36us > > NOTE: For Intel E5-2620 v2 (2-way) TurboBoost mode, there is up to > 60us latency on the same package mwait C2 and mwait C3 latency test > (well, I don't know why). > > If your application is latency aware, you need to be careful with the > deep mwait C-states. > > -------- > > There are cases that you could save more power and your system runs > faster! The situation I found is that deep mwait C-states could allow > loaded CPU to boost to higher frequency. Here is what I saw on Intel > E5-2620 v2 (2-way) (ACPI P-state 2101 TurboBoost): > > make -j 48 -DNO_MODULES buildkernel KERNCONF=LINT64 > > Force mwait C1/0 on all CPUs. Total time: 182s > Power consumption during make depend: 110w > CPU frequency during make depend: 2.37GHz > Power consumption during full run: 161w > CPU frequency during full run: 2.4GHz > > Force mwait C3/0 on all CPUs. Total time: 180s (2 seconds shorter!) > Power consumption during make depend: 106w (4w lower!) > CPU frequency during make depend: 2.57GHz (200MHz higher!) > Power consumption during full run: 161w (same) > CPU frequency during full run: 2.4GHz > > Best Regards, > sephe > > -- > Tomorrow Will Never Die > -- Bob Bishop r...@gid.co.uk
