Haswell CPU - Never enters C6 or C7?

sctyboy · 2014-04-11 01:33:23

I'm using kernel 3.14 with the default scaling_driver (intel_pstate), my CPU never enters C6 or C7 (according to i7z and turbostat, outputs below).

Motherboard: ASRock Z87E-ITX, CPU: Core i5-4570S

I confirmed that all the relevant C-states are enabled in the BIOS, but I don't know what else to do. If I boot with intel_pstate=disabled the result is the same.

[root@scottylinux ~]# turbostat sleep 2
cor CPU %c0 GHz TSC SMI %c1 %c3 %c6 %c7 CTMP PTMP %pc2 %pc3 %pc6 %pc7 Pkg_W Cor_W GFX_W
1.44 0.83 2.90 0 0.17 98.39 0.00 0.00 37 38 93.72 0.00 0.00 0.00 13.97 1.61 0.00
0 0 1.05 0.80 2.90 0 0.18 98.77 0.00 0.00 37 38 93.72 0.00 0.00 0.00 13.97 1.61 0.00
1 1 2.87 0.86 2.90 0 0.14 96.99 0.00 0.00 37
2 2 0.82 0.81 2.90 0 0.16 99.02 0.00 0.00 34
3 3 1.00 0.80 2.90 0 0.21 98.79 0.00 0.00 36

Socket [0] - [physical cores=4, logical cores=4, max online cores ever=4]
TURBO ENABLED on 4 Cores, Hyper Threading OFF
Max Frequency without considering Turbo 2997.93 MHz (99.93 x [30])
Max TURBO Multiplier (if Enabled) with 1/2/3/4 Cores is 36x/35x/33x/32x
Real Current Frequency 820.06 MHz [99.93 x 8.21] (Max of below)
Core [core-id] :Actual Freq (Mult.) C0% Halt(C1)% C3 % C6 % C7 % Temp VCore
Core 1 [0]: 820.06 (8.21x) 7.62 6.61 91.2 0 0 36 0.7239
Core 2 [1]: 807.20 (8.08x) 1 1.13 98.7 0 0 36 0.7239
Core 3 [2]: 797.70 (7.98x) 1 0.267 99.7 0 0 34 0.7225
Core 4 [3]: 808.25 (8.09x) 1 1.36 98.5 0 0 37 0.7201

graysky · 2014-06-02 23:36:10

You're in good company. Mine can go into C3 but nothing lower despite it being enabled in the BIOS. Some PSUs do not support these states, but mine does. Perhaps a kernel bug?

i7z-git

Cpu speed from cpuinfo 2900.00Mhz
cpuinfo might be wrong if cpufreq is enabled. To guess correctly try estimating via tsc
Linux's inbuilt cpu_khz code emulated now
True Frequency (without accounting Turbo) 2899 MHz
  CPU Multiplier 29x || Bus clock frequency (BCLK) 99.97 MHz

Socket [0] - [physical cores=2, logical cores=4, max online cores ever=2]
  TURBO DISABLED on 2 Cores, Hyper Threading ON
  Max Frequency without considering Turbo 2899.00 MHz (99.97 x [29])
  Max TURBO Multiplier (if Enabled) with 1/2/3/4 Cores is  29x/29x/29x/29x
  Real Current Frequency 799.76 MHz [99.97 x 8.00] (Max of below)
        Core [core-id]  :Actual Freq (Mult.)      C0%   Halt(C1)%  C3 %   C6 %   C7 %  Temp      VCore
        Core 1 [0]:       799.76 (8.00x)        1.36    1.88    97.7       0       0    34      0.6707
        Core 2 [1]:       799.61 (8.00x)        1.38    1.22    98.4       0       0    32      0.6731

turbostat

    Core     CPU Avg_MHz   %Busy Bzy_MHz TSC_MHz     SMI  CPU%c1  CPU%c3  CPU%c6  CPU%c7 CoreTmp  PkgTmp Pkg%pc2 Pkg%pc3 Pkg%pc6 Pkg%pc7 PkgWatt CorWatt GFXWatt 
       -       -      28    3.56     800    2900       0    4.41   92.02    0.00    0.00      35      40   45.90    0.00    0.00    0.00   10.02    0.26    4.80
       0       0      20    2.56     800    2900       0    9.02   88.42    0.00    0.00      35      40   45.90    0.00    0.00    0.00   10.02    0.26    4.80
       0       2      65    8.07     800    2900       0    3.51
       1       1      22    2.75     800    2900       0    1.62   95.63    0.00    0.00      35
       1       3       7    0.87     800    2900       0    3.50

graysky · 2014-06-03 19:04:51

...are any Haswell users out there able to enter C6 states?

Gusar · 2014-06-04 11:42:46

Yep, C6 and C7. Gigabyte B85M-HD3 motherboard, Core i5-4570S CPU

    Core     CPU Avg_MHz   %Busy Bzy_MHz TSC_MHz     SMI  CPU%c1  CPU%c3  CPU%c6  CPU%c7 CoreTmp  PkgTmp Pkg%pc2 Pkg%pc3 Pkg%pc6 Pkg%pc7 PkgWatt CorWatt GFXWatt 
       -       -       2    0.28     798    2893       0    0.57    1.51    0.03   97.60      31      32   96.90    0.00    0.00    0.00    8.15    0.03    0.00
       0       0       3    0.39     798    2893       0    0.08    0.00    0.00   99.53      31      32   96.90    0.00    0.00    0.00    8.15    0.03    0.00
       1       1       3    0.41     798    2893       0    2.04    0.05    0.02   97.48      28
       2       2       1    0.13     798    2893       0    0.05    0.00    0.00   99.82      28
       3       3       2    0.21     798    2893       0    0.10    6.01    0.12   93.55      29

graysky · 2014-06-04 12:01:38

If I boot into ubuntu, I am able to enter C7 just fine; also if I boot to a fresh install of Arch on another partition, I am able to get into C7 just fine... I am open to suggestions to help figure out what could be keeping me from getting into C6/C7.

Last edited by graysky (2014-06-04 20:51:01)

graysky · 2014-06-04 21:00:04

After much troubleshooting, disabling services, etc, I found out what is keeping me out of C6 and C7: setting my mtu size to something non-standard! I have a start up script that simply runs this:

/usr/bin/ip link set eno1 mtu 4000

If I manually switch the mtu size back to 1500 (the default) I am able to enter C6 and C7. Bug with the net driver I suspect which is e1000e for me.

Cpu speed from cpuinfo 2899.00Mhz
cpuinfo might be wrong if cpufreq is enabled. To guess correctly try estimating via tsc
Linux's inbuilt cpu_khz code emulated now
True Frequency (without accounting Turbo) 2899 MHz
  CPU Multiplier 29x || Bus clock frequency (BCLK) 99.97 MHz

Socket [0] - [physical cores=2, logical cores=4, max online cores ever=2]
  TURBO DISABLED on 2 Cores, Hyper Threading ON
  Max Frequency without considering Turbo 2899.00 MHz (99.97 x [29])
  Max TURBO Multiplier (if Enabled) with 1/2/3/4 Cores is  29x/29x/29x/29x
  Real Current Frequency 799.72 MHz [99.97 x 8.00] (Max of below)
        Core [core-id]  :Actual Freq (Mult.)      C0%   Halt(C1)%  C3 %   C6 %   C7 %  Temp      VCore
        Core 1 [0]:       799.72 (8.00x)        3.76    10.6    1.96    2.78    83.6    37      0.6707
        Core 2 [1]:       799.72 (8.00x)        4.51     4.9       1       0    92.9    35      0.6682





C0 = Processor running without halting
C1 = Processor running with halts (States >C0 are power saver modes with cores idling)
C3 = Cores running with PLL turned off and core cache turned off
C6, C7 = Everything in C3 + core state saved to last level cache, C7 is deeper than C6
  Above values in table are in percentage over the last 1 sec
[core-id] refers to core-id number in /proc/cpuinfo
'Garbage Values' message printed when garbage values are read
  Ctrl+C to exit

EDIT: This is not a bug, it is by design: https://bugzilla.kernel.org/show_bug.cgi?id=77361

Last edited by graysky (2014-11-27 16:50:36)

k0tb4tzen · 2015-07-18 00:04:19

I don't have an MTU different from 1500, but my CPU doesn't enter C7, too.

I have an i7 4790K and a Gigabyte H97 Mainboard.

WorMzy · 2015-07-19 10:11:39

k0tb4tzen, please don't necrobump.

https://wiki.archlinux.org/index.php/Fo … bumping.22

Open a new topic and link back to this one if you feel it is still relevant.

Closing.

Arch Linux

#1 2014-04-11 01:33:23

Haswell CPU - Never enters C6 or C7?

#2 2014-06-02 23:36:10

Re: Haswell CPU - Never enters C6 or C7?

#3 2014-06-03 19:04:51

Re: Haswell CPU - Never enters C6 or C7?

#4 2014-06-04 11:42:46

Re: Haswell CPU - Never enters C6 or C7?

#5 2014-06-04 12:01:38

Re: Haswell CPU - Never enters C6 or C7?

#6 2014-06-04 21:00:04

Re: Haswell CPU - Never enters C6 or C7?

#7 2015-07-18 00:04:19

Re: Haswell CPU - Never enters C6 or C7?

#8 2015-07-19 10:11:39

Re: Haswell CPU - Never enters C6 or C7?

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