RE: [RFC/RFT][PATCH v6] cpuidle: New timer events oriented governor for tickless systems

[Doug Smythies]

On 2018.12.03 03:48 Rafael J. Wysocki wrote:

>>> There is an additional issue where if idle state 0 is disabled (with the above suggested code patch),
>>> idle state usage seems to fall to deeper states than idle state 1.
>>> This is not the expected behaviour.
>> 
>> No, it isn't.
>> 
>>> Kernel 4.20-rc3 works as expected.
>>> I have not figured this issue out yet, in the code.
>>>
>>> Example (1 minute per sample. Number of entries/exits per state):
>>>     State 0     State 1     State 2     State 3     State 4    Watts
>>>    28235143,         83,         26,         17,        837,  64.900
>>>     5583238,     657079,    5884941,    8498552,   30986831,  62.433 << Transition sample, after idle state 0 disabled
>>>           0,     793517,    7186099,   10559878,   38485721,  61.900 << ?? should have all gone into Idle state 1
>>>           0,     795414,    7340703,   10553117,   38513456,  62.050
>>>           0,     807028,    7288195,   10574113,   38523524,  62.167
>>>           0,     814983,    7403534,   10575108,   38571228,  62.167
>>>           0,     838302,    7747127,   10552289,   38556054,  62.183
>>>     9664999,     544473,    4914512,    6942037,   25295361,  63.633 << Transition sample, after idle state 0 enabled
>>>    27893504,         96,         40,          9,        912,  66.500
>>>    26556343,         83,         29,          7,        814,  66.683
>>>    27929227,         64,         20,         10,        931,  66.683
>> 
>> I see.
>> 
>> OK, I'll look into this too, thanks!
>
> This probably is the artifact of the fix for the teo_find_shallower_state()
> issue.
>
> Anyway, I'm not able to reproduce this with the teo_find_shallower_state() issue
> fixed differently.

I am not able to reproduce with your teo_find_shallower_state(), or teo V 7,
either. Everything is graceful now, as states are disabled:
(10 seconds per sample. Number of entries/exits per state):

    State 0     State 1     State 2     State 3     State 4    Watts
          0,          6,          4,          1,        414,   3.700
          2,          4,         30,          3,        578,   3.700  << No load
     168619,         37,         39,          4,        480,   5.600  << Transition sample
    4643618,         45,          8,          1,        137,  61.200  << All idle states enabled
    4736227,         40,          3,          5,        111,  61.800
    1888417,    4369314,         25,          2,         89,  62.000  << Transition sample
          0,    7266864,          9,          0,          0,  62.200  << state 0 disabled
          0,    7193372,          9,          0,          0,  62.700
          0,    5539898,    1744007,          0,          0,  63.500  << Transition sample
          0,          0,    8152956,          0,          0,  63.700  << states 0,1 disabled
          0,          0,    8015151,          0,          0,  63.900
          0,          0,    4146806,    6349619,          0,  63.000  << Transition sample
          0,          0,          0,   13252144,          0,  61.600  << states 0,1,2 disabled
          0,          0,          0,   13258313,          0,  61.800
          0,          0,          0,   10417428,    1984451,  61.200  << Transition sample
          0,          0,          0,          0,    9247172,  58.500  << states 0,1,2,3 disabled
          0,          0,          0,          0,    9242657,  58.500
          0,          0,          0,          0,    9233749,  58.600
          0,          0,          0,          0,    9238444,  58.700
          0,          0,          0,          0,    9236345,  58.600

For reference, this is kernel 4.20-rc5 (with your other proposed patches):

    State 0     State 1     State 2     State 3     State 4    Watts
          0,          4,          8,          6,        426,   3.700
    1592870,        279,        149,         96,        831,  21.800
    5071279,        154,         25,          6,        105,  61.200
    5095090,         78,         21,          1,         86,  61.800
    5001493,         94,         30,          4,        101,  62.200
     616019,    5446924,          5,          3,         38,  62.500
          0,    6249752,          0,          0,          0,  63.300
          0,    6293671,          0,          0,          0,  63.800
          0,    3751035,    2529964,          0,          0,  64.100
          0,          0,    6101167,          0,          0,  64.500
          0,          0,    6172526,          0,          0,  64.700
          0,          0,    6163797,          0,          0,  64.900
          0,          0,    1724841,    9567528,          0,  63.300
          0,          0,          0,   13349668,          0,  62.700
          0,          0,          0,   13360471,          0,  62.700
          0,          0,          0,   13355424,          0,  62.700
          0,          0,          0,    8854491,    3132640,  61.600
          0,          0,          0,          0,    9302824,  59.000
          0,          0,          0,          0,    9303561,  58.900
          0,          0,          0,          0,    9313397,  59.000
          0,          0,          0,          0,    9333944,  59.000

Test kernel:
94a976a cpuidle: New timer events oriented governor for tickless systems  <<< V7
935be4e cpuidle: poll_state: Disregard disable idle states
e3670df cpuidle: Add 'high' and 'low' idle state metrics
dfa672c Documentation: admin-guide: PM: Add cpuidle document
2595646 Linux 4.20-rc5

Reference kernel:
f418681 cpuidle: poll_state: Disregard disable idle states
1be0e87 cpuidle: Add 'high' and 'low' idle state metrics
279ec1d Documentation: admin-guide: PM: Add cpuidle document
2595646 Linux 4.20-rc5

... Doug