Linux CPU电源管理 P-state

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承接上文C-state

上文说了除了使用C-state去节能,还可以使用P-state去减排。让我们看看P-state

P-states

P-state是在C-state为C0的时候起作用,就是说当CPU执行指令的时候才有P-state的用武之地,其他条件下P-state可以摸鱼了。P-state基本上只能更改电压和CPU频率来达到减少能量消耗的目的。不同的电压与频率会产成一个极大值,这个值被称为P0。实际上就是P-state需要系统在运行状态下但是它不需要火力全开(全部性能开启)状态运行,这样P-state就可以降低电压和频率来满足系统运行即可。其的中心思想就是节俭,正所谓上舞厅吃爆米花,该省的省,该花的花。

谁可以控制P-state

OS-controlled

系统比较在意P-state,并且设置了一个特定P-state。基本上是当选择一个CPU频率,会使CPU更改电压以满足给定的CPU频率,时钟生成器也锁定到这个特定的CPU频率。

HW-controlled

一句话,P-state会根据HW的支持来更改P-state,也就是HWP。OS只发送工作负载要求不参与更改P-state。本文下方信息中有关于此硬件辅助功能的输出。

超频 (Intel® Turbo Boost)

顾名思义,这项技术就是由于TDP(thermal design power)是CPU可以运行的最大功率,当功耗小于此值并且在特定条件下,CPU的频率可以超过基础频率(803 ~ 2711MHZ 本机频率范围)。Turbo Boost可以临时的增涨功率到PL2 (本机的 130W)但只能持续很短的时间。

CPU特性一窥

我就知道你们喜欢这个环节,上酸菜:

Processor                            [Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz]                                                                              
|- Architecture                                                      [Skylake/S]                                                                              
|- Vendor ID                                                      [GenuineIntel]                                                                              
|- Microcode                                                        [0x000000ea]                                                                              
|- Signature                                                           [  06_5E]                                                                              
|- Stepping                                                            [      3]                                                                              
|- Online CPU                                                          [  8/  8]                                                                              
|- Base Clock                                                          [100.438]                                                                              
|- Frequency            (MHz)                      Ratio                                                                                                      
                 Min    803.51                    <   8 >                                                                                                     
                 Max   2711.83                    <  27 >                                                                                                     
|- Factory                                                             [100.000]                                                                              
                       2700                       [  27 ]                                                                                                     
|- Performance                                                                                                                                                
   |- P-State                                                                                                                                                 
                 TGT    803.51                    <   8 >                                                                                                     
   |- HWP                                                                                                                                                     
                 Min    803.51                    <   8 >                                                                                                     
                 Max   3615.77                    <  36 >                                                                                                     
                 TGT      AUTO                    <   0 >                                                                                                     
|- Turbo Boost                                                         [ UNLOCK]                                                                              
                  1C   3615.77                    <  36 >                                                                                                     
                  2C   3414.90                    <  34 >                                                                                                     
                  3C   3314.46                    <  33 >                                                                                                     
                  4C   3214.02                    <  32 >                                                                                                     
|- Uncore                                                              [ UNLOCK]                                                                              
                 Min    803.51                    <   8 >                                                                                                     
                 Max   3615.77                    <  36 >                                                                                                     
|- TDP                                       evel <  0:3  >
   |- Programmable                                                     [ UNLOCK]                                                                              
   |- Configuration                                                    [ UNLOCK]                                                                              
   |- Turbo Activation                                                 [ UNLOCK]
             Nominal   2711.83                    [  27 ]                        
              Level1   2209.64                    [  22 ]                        
               Turbo   3515.34                    <  35 >                        

Instruction Set Extensions                                                       
|- 3DNow!/Ext [N/N]          ADX [Y]          AES [Y]  AVX/AVX2 [Y/Y] 
|- AVX512-F     [N]    AVX512-DQ [N]  AVX512-IFMA [N]   AVX512-PF [N] 
|- AVX512-ER    [N]    AVX512-CD [N]    AVX512-BW [N]   AVX512-VL [N] 
|- AVX512-VBMI  [N] AVX512-VBMI2 [N]  AVX512-VNMI [N]  AVX512-ALG [N] 
|- AVX512-VPOP  [N] AVX512-VNNIW [N] AVX512-FMAPS [N] AVX512-VP2I [N] 
|- AVX512-BF16  [N]  BMI1/BMI2 [Y/Y]         CLWB [N] CLFLUSH/O [Y/Y] 
|- CLAC-STAC    [Y]         CMOV [Y]    CMPXCHG8B [Y]  CMPXCHG16B [Y] 
|- F16C         [Y]          FPU [Y]         FXSR [Y]   LAHF-SAHF [Y] 
|- MMX/Ext    [Y/N] MON/MWAITX [Y/N]        MOVBE [Y]   PCLMULQDQ [Y] 
|- POPCNT       [Y]       RDRAND [Y]       RDSEED [Y]      RDTSCP [Y] 
|- SEP          [Y]          SHA [N]          SSE [Y]        SSE2 [Y] 
|- SSE3         [Y]        SSSE3 [Y]  SSE4.1/4A [Y/N]      SSE4.2 [Y] 
|- SERIALIZE    [N]      SYSCALL [Y]          SGX [Y]       RDPID [N] 

Features                                                                         
|- 1 GB Pages Support                                      1GB-PAGES   [Capable]
|- Advanced Configuration & Power Interface                     ACPI   [Capable]
|- Advanced Programmable Interrupt Controller                   APIC   [Capable]
|- APIC Timer Invariance                                        ARAT   [Capable]
|- Core Multi-Processing                                  CMP Legacy   [Missing]
|- L1 Data Cache Context ID                                  CNXT-ID   [Missing]
|- Direct Cache Access                                           DCA   [Missing]
|- Debugging Extension                                            DE   [Capable]
|- Debug Store & Precise Event Based Sampling               DS, PEBS   [Capable]
|- CPL Qualified Debug Store                                  DS-CPL   [Capable]
|- 64-Bit Debug Store                                         DTES64   [Capable]
|- Fast-String Operation                                Fast-Strings   [Capable]
****** Feature 太多略过 ********
Technologies                                                                     
|- Data Cache Unit                                                               
   |- L1 Prefetcher                                                L1 HW   < ON>
   |- L1 IP Prefetcher                                          L1 HW IP   < ON>
   |- L2 Prefetcher                                                L2 HW   < ON>
   |- L2 Line Prefetcher                                        L2 HW CL   < ON>
|- System Management Mode                                       SMM-Dual   [ ON]
|- Hyper-Threading                                                   HTT   [ ON]
|- SpeedStep                                                        EIST   < ON>
|- Dynamic Acceleration                                              IDA   [ ON]
|- Turbo Boost                                                     TURBO   < ON>
|- Energy Efficiency Optimization                                    EEO   < ON>
|- Race To Halt Optimization                                         R2H   < ON>
|- Watchdog Timer                                                    TCO   < ON>
|- Virtualization                                                    VMX   [ ON]
   |- I/O MMU                                                       VT-d   [ ON]
   |- Version                                                     [         1.0]
   |- Hypervisor                                                           [OFF]
   |- Vendor ID                                                   [         N/A]

Performance Monitoring                                                           
|- Version                                                        PM       [  4]
|- Counters:          General                   Fixed                            
|                     4 x 48 bits             3 x 48 bits                        
|- Enhanced Halt State                                           C1E       <OFF>
|- C1 Auto Demotion                                              C1A       < ON>
|- C3 Auto Demotion                                              C3A       < ON>
|- C1 UnDemotion                                                 C1U       < ON>
|- C3 UnDemotion                                                 C3U       < ON>
|- C6 Core Demotion                                              CC6       <OFF>
|- C6 Module Demotion                                            MC6       <OFF>
|- Legacy Frequency ID control                                   FID       [OFF]
|- Legacy Voltage ID control                                     VID       [OFF]
|- P-State Hardware Coordination Feedback                MPERF/APERF       [ ON]
|- Hardware-Controlled Performance States                        HWP       < ON>
   |- Capabilities      (MHz)                      Ratio                         
              Lowest    100.44                    [   1 ]                        
           Efficient    803.51                    [   8 ]                        
          Guaranteed   2711.83                    [  27 ]                        
             Highest   3615.78                    [  36 ]                        
|- Hardware Duty Cycling                                         HDC       < ON>
|- Package C-States                                                              
   |- Configuration Control                                   CONFIG   [   LOCK]
   |- Lowest C-State                                           LIMIT   <     C8>
   |- I/O MWAIT Redirection                                  IOMWAIT   <Disable>
   |- Max C-State Inclusion                                    RANGE   <     C8>
|- Core C-States                                                                 
   |- C-States Base Address                                      BAR   [ 0x1814]
|- MONITOR/MWAIT                                                                 
   |- State index:    #0    #1    #2    #3    #4    #5    #6    #7               
   |- Sub C-State:     0     2     1     2     4     1     1     1               
|- Core Cycles                                                         [Capable]
|- Instructions Retired                                                [Capable]
|- Reference Cycles                                                    [Capable]
|- Last Level Cache References                                         [Capable]
|- Last Level Cache Misses                                             [Capable]
|- Branch Instructions Retired                                         [Capable]
|- Branch Mispredicts Retired                                          [Capable]
|- Top-down slots Counter                                              [Capable]
Power, Current & Thermal                                                         
|- Clock Modulation                                             ODCM   <Disable>
   |- DutyCycle                                                        [  0.00%]
|- Power Management                                         PWR MGMT   [   LOCK]
   |- Energy Policy                                        Bias Hint   <      6>
   |- Energy Policy                                          HWP EPP   <    128>
|- Temperature Offset:Junction                                 TjMax [  3:100 C]
|- Digital Thermal Sensor                                        DTS   [Capable]
|- Power Limit Notification                                      PLN   [Capable]
|- Package Thermal Management                                    PTM   [Capable]
|- Thermal Monitor 1                                             TM1   [ Enable]
|- Thermal Monitor 2                                             TM2   [Capable]
|- Thermal Design Power                                          TDP   [   45 W]
   |- Minimum Power                                              Min   [Missing]
   |- Maximum Power                                              Max   [Missing]
|- Thermal Design Power                                      Package   < Enable>
   |- Power Limit (28 sec)                                       PL1   <   45 W>
   |- Power Limit (1 sec)                                        PL2   <   56 W>
|- Thermal Design Power                                         Core   <Disable>
   |- Power Limit                                                PL1   [Missing]
|- Thermal Design Power                                       Uncore   <Disable>
   |- Power Limit                                                PL1   [Missing]
|- Thermal Design Power                                         DRAM   <Disable>
   |- Power Limit                                                PL1   [Missing]
|- Thermal Design Power                                     Platform   < Enable>
   |- Power Limit (28 sec)                                       PL1   <   45 W>
   |- Power Limit (1 sec)                                        PL2   <  130 W>
|- Electrical Design Current                                     EDC   [Missing]
|- Thermal Design Current                                        TDC   [Missing]
|- Core Thermal Point                                                            
   |- DTS Threshold #1                                     Threshold   [Missing]
   |- DTS Threshold #2                                     Threshold   [Missing]
|- Package Thermal Point                                                         
   |- DTS Threshold #1                                     Threshold   [Missing]
   |- DTS Threshold #2                                     Threshold   [Missing]

上面输出中可以找到P-state与C-state对应信息,以及Turbo Boost等相关数据

CPU的当前频率与电压:

CPU Freq(MHz) VID  Min     Vcore   Max
000   34.30     0  0.0000  0.0000  0.0000
001   13.65  7835  0.6978  0.9564  1.2351
002   77.69     0  0.0000  0.0000  0.0000
003   12.96     0  0.0000  0.0000  0.0000
004   33.66     0  0.0000  0.0000  0.0000
005   16.38     0  0.0000  0.0000  0.0000
006   18.85     0  0.0000  0.0000  0.0000
007   17.84     0  0.0000  0.0000  0.0000

###总结 现在大部分机器已经使用硬件辅助来优化P-state,可共用户操作空间有限,看到这里是不是感觉白学了,那就对了,越来越多的技术会被硬件替代,就像自动化代替了手工劳动一样,我们只能被滚滚的历史车轮碾压,或者努力学习裸奔在被碾压的路上。

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