我想在基于 Ubuntu 20.04 的系统（KDE neon）上设置更高的 CPU 频率，内核为 5.4.0-58-generic。CPU 是 Intel(R) Core(TM) i7-8700，硬件限制为 800 MHz - 4.60 GHz。
环境
sudo cpupower frequency-set --min 4500Hz
按照建议这里不起作用。频率仍然在 800 MHz 和 4.60 GHz 范围内。
cpufreq-info 的示例输出为：
analyzing CPU 11:
driver: intel_pstate
CPUs which run at the same hardware frequency: 11
CPUs which need to have their frequency coordinated by software: 11
maximum transition latency: 4294.55 ms.
hardware limits: 800 MHz - 4.60 GHz
available cpufreq governors: performance, powersave
current policy: frequency should be within 800 MHz and 4.60 GHz.
The governor "performance" may decide which speed to use
within this range.
current CPU frequency is 4.21 GHz.
对于所有核心。
改变scaling_min_freq也无济于事：
MAX_CPU=$((`nproc --all` - 1))
for i in $(seq 0 $MAX_CPU); do
echo 4500000 | sudo tee /sys/devices/system/cpu/cpu$i/cpufreq/scaling_min_freq
done
示例输出cpufreq-info
analyzing CPU 11:
driver: intel_pstate
CPUs which run at the same hardware frequency: 11
CPUs which need to have their frequency coordinated by software: 11
maximum transition latency: 4294.55 ms.
hardware limits: 800 MHz - 4.60 GHz
available cpufreq governors: performance, powersave
current policy: frequency should be within 4.50 GHz and 4.60 GHz.
The governor "performance" may decide which speed to use
within this range.
current CPU frequency is 4.23 GHz.
虽然频率应该在 4.50 GHz 和 4.60 GHz 之间，但当前 CPU 频率仍为 4.23 GHz。看来这 scaling_min_freq 仅用于打印信息，并没有真正改变性能调节器。
我也试过pstate-frequency：
sudo pstate-frequency -S -p max
pstate-frequency version 3.11.0
pstate::CPU_DRIVER -> intel_pstate
pstate::CPU_GOVERNOR -> performance
pstate::TURBO -> 0 [ON]
pstate::CPU_MIN -> 99% [4554000KHz]
pstate::CPU_MAX -> 100% [4600000KHz]
但这再次只是改变scaling_min_freq，而 cpufreq-info 的输出仍然不明确
analyzing CPU 11:
driver: intel_pstate
CPUs which run at the same hardware frequency: 11
CPUs which need to have their frequency coordinated by software: 11
maximum transition latency: 4294.55 ms.
hardware limits: 800 MHz - 4.60 GHz
available cpufreq governors: performance, powersave
current policy: frequency should be within 4.55 GHz and 4.60 GHz.
The governor "performance" may decide which speed to use
within this range.
current CPU frequency is 4.24 GHz.
除了使用遗留cpufreq_userspace驱动程序相反intel_pstate，有没有办法设置更高的最小（或更好的恒定）CPU频率？
答案1
处理器可以自行降低 CPU 频率，即使在性能模式下也是如此。在性能模式下，启用 HWP 后，您应该无法检测到任何性能下降。另请注意，调整各种最小值不会对性能模式产生任何影响。
现在，如果确实希望始终获得准确的 CPU 报告频率，那么可以使用以下方法：
首先，您必须处理最大 CPU 频率作为活动核心的函数。如果您不要求 Turbostat 保持安静，它将为您列出此信息。示例 1 (i7-2600K)：
$ sudo turbostat
...
cpu5: MSR_TURBO_RATIO_LIMIT: 0x23242526
35 * 100.0 = 3500.0 MHz max turbo 4 active cores
36 * 100.0 = 3600.0 MHz max turbo 3 active cores
37 * 100.0 = 3700.0 MHz max turbo 2 active cores
38 * 100.0 = 3800.0 MHz max turbo 1 active cores
因此，即使我将最低 CPU 频率设置为 3.8 GHz，处理器本身也会根据活动核心的功能覆盖该频率。因此，我必须将最高 CPU 频率设置为 3.5 GHz 以避免此问题。
示例 2（i5-9600K）：
cpu5: MSR_TURBO_RATIO_LIMIT: 0x2b2b2e2e2e2e2e2e
43 * 100.0 = 4300.0 MHz max turbo 8 active cores << I only have 6 cores
43 * 100.0 = 4300.0 MHz max turbo 7 active cores << I only have 6 cores
46 * 100.0 = 4600.0 MHz max turbo 6 active cores
46 * 100.0 = 4600.0 MHz max turbo 5 active cores
46 * 100.0 = 4600.0 MHz max turbo 4 active cores
46 * 100.0 = 4600.0 MHz max turbo 3 active cores
46 * 100.0 = 4600.0 MHz max turbo 2 active cores
46 * 100.0 = 4600.0 MHz max turbo 1 active cores
请注意，我已将其设置为不根据活动核心来降低 CPU 频率。
免责声明：除非您确定您的系统能够处理热量和电流要求，否则请勿执行此操作。还需要解锁的处理器。
现在，即使如此，性能模式下 CPU 频率也可能不会保持在 4.6 GHz：
$ sudo turbostat --Summary --quiet --show Busy%,Bzy_MHz,IRQ,PkgWatt,PkgTmp --interval 10
Busy% Bzy_MHz IRQ PkgTmp PkgWatt
0.14 4579 650 32 2.10 <<<
0.40 4600 507 32 2.27
0.09 4600 270 31 2.01
0.13 4600 322 32 2.10
0.02 4600 205 31 1.99
0.11 4600 229 32 2.04
0.10 4600 269 32 2.02
0.08 4600 300 32 2.00
0.04 4598 443 32 2.01
0.05 4600 215 32 1.98
0.02 4586 210 32 1.95 <<
0.05 4594 233 32 1.97 <<
0.01 4600 246 32 1.95
可以通过完全禁用空闲状态来消除此问题，但会消耗大量电量：
$ echo 1 | sudo tee /sys/devices/system/cpu/cpu*/cpuidle/state*/disable
。
$ sudo turbostat --Summary --quiet --show Busy%,Bzy_MHz,IRQ,PkgWatt,PkgTmp --interval 10
Busy% Bzy_MHz IRQ PkgTmp PkgWatt
100.26 4600 60109 47 52.88 <<< not 100% busy, but 100% idle state 0
100.26 4600 60113 48 53.01 <<< if no idle states enabled the kernel will use 0.
100.26 4600 60107 48 53.01
100.26 4600 60183 48 53.01
好的，但是还有另一种方法。事实证明空闲状态 2 是 HWP 的问题，所以只需禁用它即可：
doug@s18:~/idle$ echo 1 | sudo tee /sys/devices/system/cpu/cpu*/cpuidle/state*/disable
1
doug@s18:~/idle$ sudo ~/c/msr-decoder^C
doug@s18:~/idle$ echo 0 | sudo tee /sys/devices/system/cpu/cpu*/cpuidle/state*/disable
0
doug@s18:~/idle$ echo 1 | sudo tee /sys/devices/system/cpu/cpu*/cpuidle/state2/disable
1
doug@s18:~/idle$ grep . /sys/devices/system/cpu/cpu3/cpuidle/state*/disable
/sys/devices/system/cpu/cpu3/cpuidle/state0/disable:0
/sys/devices/system/cpu/cpu3/cpuidle/state1/disable:0
/sys/devices/system/cpu/cpu3/cpuidle/state2/disable:1
/sys/devices/system/cpu/cpu3/cpuidle/state3/disable:0
/sys/devices/system/cpu/cpu3/cpuidle/state4/disable:0
/sys/devices/system/cpu/cpu3/cpuidle/state5/disable:0
/sys/devices/system/cpu/cpu3/cpuidle/state6/disable:0
/sys/devices/system/cpu/cpu3/cpuidle/state7/disable:0
/sys/devices/system/cpu/cpu3/cpuidle/state8/disable:0
。
$ sudo turbostat --Summary --quiet --show Busy%,Bzy_MHz,IRQ,PkgWatt,PkgTmp --interval 10
Busy% Bzy_MHz IRQ PkgTmp PkgWatt
0.02 4600 332 35 1.96
0.03 4600 209 35 1.94
0.09 4600 290 35 2.00
0.17 4600 377 35 2.07
0.03 4600 205 34 1.94
0.05 4600 192 35 1.95
0.15 4600 274 35 2.04
0.04 4600 208 35 1.96
0.11 4600 279 35 2.02
0.06 4600 219 34 1.97
0.13 4600 251 34 2.03
0.03 4600 173 34 1.94
0.11 4600 343 34 2.02
0.02 4600 205 33 1.94
0.03 4600 180 34 1.94
0.04 4600 183 34 1.95
0.12 4600 250 34 2.03
0.08 4600 236 33 1.99
0.02 4600 225 34 1.94
0.02 4600 165 34 1.93
0.01 4600 173 33 1.93
0.01 4600 170 33 1.93
0.02 4600 200 33 1.95
0.02 4600 199 33 1.94
0.02 4600 218 33 1.94
0.01 4600 161 33 1.93
0.01 4600 170 33 1.94
0.01 4600 187 33 1.94
0.02 4600 218 33 1.95
0.02 4600 176 33 1.94
0.01 4600 212 32 1.94
为了完整性，请使用没有 HWP 的 i7-2600K。
$ grep . /sys/devices/system/cpu/cpu3/cpufreq/*
/sys/devices/system/cpu/cpu3/cpufreq/affected_cpus:3
/sys/devices/system/cpu/cpu3/cpufreq/cpuinfo_max_freq:3800000
/sys/devices/system/cpu/cpu3/cpufreq/cpuinfo_min_freq:1600000
/sys/devices/system/cpu/cpu3/cpufreq/cpuinfo_transition_latency:20000
/sys/devices/system/cpu/cpu3/cpufreq/related_cpus:3
/sys/devices/system/cpu/cpu3/cpufreq/scaling_available_governors:ondemand performance schedutil
/sys/devices/system/cpu/cpu3/cpufreq/scaling_cur_freq:1605486
/sys/devices/system/cpu/cpu3/cpufreq/scaling_driver:intel_cpufreq
/sys/devices/system/cpu/cpu3/cpufreq/scaling_governor:ondemand
/sys/devices/system/cpu/cpu3/cpufreq/scaling_max_freq:3800000
/sys/devices/system/cpu/cpu3/cpufreq/scaling_min_freq:1600000
/sys/devices/system/cpu/cpu3/cpufreq/scaling_setspeed:<unsupported>
doug@s15:~/diag$ grep . /sys/devices/system/cpu/cpu3/cpufreq/*^C
doug@s15:~/diag$ echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
performance
doug@s15:~/diag$ echo 3500000 | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq
3500000
doug@s15:~/diag$ sudo turbostat --Summary --quiet --show Busy%,Bzy_MHz,IRQ,PkgWatt,PkgTmp --interval 10
Busy% Bzy_MHz IRQ PkgTmp PkgWatt
0.02 1806 453 28 3.75
0.02 1889 340 28 3.73
0.01 1896 268 31 3.72
0.02 1771 437 28 3.73
嘿，为什么 CPU 频率不稳定？嗯，对于非 HWP 处理器，只有禁用所有空闲状态的方法才有效。通过设置能效偏差（仅在非 HWP 模式下使用）可以获得一点响应提升：
$ cat /sys/devices/system/cpu/cpu3/power/energy_perf_bias
6
doug@s15:~/diag$ echo 0 | sudo tee /sys/devices/system/cpu/cpu3/power/energy_perf_bias
0
$ echo 1 | sudo tee /sys/devices/system/cpu/cpu*/cpuidle/state*/disable
。
$ sudo turbostat --Summary --quiet --show Busy%,Bzy_MHz,IRQ,PkgWatt,PkgTmp --interval 10
Busy% Bzy_MHz IRQ PkgTmp PkgWatt
100.00 3500 20114 52 49.06
100.00 3500 20146 54 49.49
100.00 3500 20096 58 49.87
100.00 3500 20086 59 50.17
100.00 3500 22609 61 50.50
100.00 3500 20110 62 51.02
100.00 3500 20105 63 51.53
100.00 3500 20081 65 51.78
100.00 3500 20059 66 52.02
100.00 3500 20090 67 52.23
100.00 3500 20717 68 52.37
100.00 3500 20066 68 52.48
100.00 3500 20074 68 52.58
100.00 3500 20222 71 52.78
100.00 3500 20109 70 52.83
100.00 3500 20075 70 52.81
100.00 3500 21040 70 52.92
100.00 3500 20066 70 52.95