Intro cpupower

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Intro cpupower

這篇介紹cpupower。

C-states versus P-states

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CPU 依據省電模式有區分為 Processor Operating States (C-states) 
與 Processor Performance States (P-states)。

C-states:
CPU 在沒有使用時可以被停用或以比較低的效能模式來運行，依據不同的
狀態可以區分成為幾種 C-state。
C-state 從 C0 (不閒置)開始，數字越高表示越省電(每一家的 CPU 定義
C-state 會稍微不同)。
CPU 的 C-state 有下面幾種。

C0 – Operating State
C1 – Halt
C1E – Enhanced Halt
C2 – Stop Grant
C2 – Stop Clock
C2E – Extended Stop Grant
C3 – Sleep
C3 – Deep Sleep
C3 – AltVID
C4 – Deeper Sleep
C4E/C5 -Enhanced Deeper Sleep
C6 – Deep Power Down
C7 – C6 + LLC may be flushed
C8 – C7 + LLC must be flushed

P-States 就是指 CPU 依據目前狀態自行調整工作頻率，用以省電。

指令1 - cpupower

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CPU 有支援哪一些指令，可以直接下cpupower

[root@localhost ~]# cpupower
Usage:  cpupower [-c|--cpu cpulist ] <command> [<args>]
Supported commands are:
        frequency-info
        frequency-set
        idle-info
        idle-set
        set
        info
        monitor
        help

Not all commands can make use of the -c cpulist option.

Use 'cpupower help <command>' for getting help for above commands.

指令2 - cpupower idle-info

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查詢CPU有支援的 C-State

[root@localhost ~]# cpupower idle-info
CPUidle driver: acpi_idle
CPUidle governor: menu
analyzing CPU 0:

Number of idle states: 2
Available idle states: POLL C1
POLL:
Flags/Description: CPUIDLE CORE POLL IDLE
Latency: 0
Usage: 0
Duration: 0
C1:
Flags/Description: ACPI HLT
Latency: 0
Usage: 4183551158
Duration: 11583728700572

指令3 - cpupower monitor -l

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參數 monitor 可以檢視目前是哪一種 C-State

[root@localhost ~]# cpupower monitor -l
Monitor "Nehalem" (4 states) - Might overflow after 922000000 s
C3      [C] -> Processor Core C3
C6      [C] -> Processor Core C6
PC3     [P] -> Processor Package C3
PC6     [P] -> Processor Package C6
Monitor "Mperf" (3 states) - Might overflow after 922000000 s
C0      [T] -> Processor Core not idle
Cx      [T] -> Processor Core in an idle state
Freq    [T] -> Average Frequency (including boost) in MHz
Monitor "Idle_Stats" (2 states) - Might overflow after 4294967295 s
POLL    [T] -> CPUIDLE CORE POLL IDLE
C1      [T] -> ACPI HLT

[root@localhost ~]# cpupower monitor
              | Nehalem                   || Mperf              || Idle_Stats
 PKG|CORE| CPU| C3   | C6   | PC3  | PC6   || C0   | Cx   | Freq  || POLL | C1
   0|   0|   0|  0.00|  0.00|  0.00|  0.00||  0.00| 100.0|9223372036854775808||  0.00| 98.54
   0|   1|   1|  0.00|  0.00|  0.00|  0.00||  0.00| 100.0|9223372036854775808||  0.00| 98.48
   0|   2|   2|  0.00|  0.00|  0.00|  0.00||  0.00| 100.0|9223372036854775808||  0.00| 98.54
   0|   3|   3|  0.00|  0.00|  0.00|  0.00||  0.00| 100.0|9223372036854775808||  0.00| 98.36
   1|   0|   4|  0.00|  0.00|  0.00|  0.00||  0.00| 100.0|9223372036854775808||  0.00| 98.65
   1|   1|   5|  0.00|  0.00|  0.00|  0.00||  0.00| 100.0|9223372036854775808||  0.00| 98.99
   1|   2|   6|  0.00|  0.00|  0.00|  0.00||  0.00| 100.0|9223372036854775808||  0.00| 98.63
   1|   3|   7|  0.00|  0.00|  0.00|  0.00||  0.00| 100.0|9223372036854775808||  0.00| 98.74

指令4 - cpupower frequency-info

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透過指令參數 frequency-info 可以得知目前這個 CPU 支援的工作頻率。

[root@localhost ~]# cpupower frequency-info
analyzing CPU 0:
  no or unknown cpufreq driver is active on this CPU
  CPUs which run at the same hardware frequency: Not Available
  CPUs which need to have their frequency coordinated by software: Not Available
  maximum transition latency:  Cannot determine or is not supported.
Not Available
  available cpufreq governors: Not Available
  Unable to determine current policy
  current CPU frequency: Unable to call hardware
  current CPU frequency:  Unable to call to kernel
  boost state support:
    Supported: yes
    Active: yes