Re: [PATCH] powerpc/vtime: Initialize starttime at boot for native accounting

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Hi Christophe. Thanks for taking a look and review.

On 6/4/26 8:42 PM, Christophe Leroy (CS GROUP) wrote:
> 

>>> Also, does this warrant Fixes tag? I found these two likely candidates.
>>> Likely this issues exists since beginning.
>>> c223c90386bc powerpc32: provide VIRT_CPU_ACCOUNTING
>>
>> You say system has 240 CPU so I suppose this is not ppc32. That commit 
>> wsa not supposed to change anything for ppc64, did you identify 
>> anything special in that commit related to ppc64 ?

Yes. this was ppc64.

>>
>>> b38a181c11d0 powerpc/time: isolate scaled cputime accounting in 
>>> dedicated functions.
>>
>> This one is also pure code re-organisation, unless you've been able to 
>> spot a particular issue ?
> 
> Maybe commit cf9efce0ce31 ("powerpc: Account time using timebase rather 
> than PURR")
> 
> It removed snapshot_timebases() and I can't see anything to replace it.
> 

Yes. But this patch is dependent on Frederic's series.
backporting that is going to be difficult. So i am thinking to avoid putting Fixes tag.


> 
>>
>>>
>>>   arch/powerpc/kernel/time.c | 4 +++-
>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
>>> index 3460d1a5a97c..11145c40183d 100644
>>> --- a/arch/powerpc/kernel/time.c
>>> +++ b/arch/powerpc/kernel/time.c
>>> @@ -377,7 +377,6 @@ void vtime_task_switch(struct task_struct *prev)
>>>       }
>>>   }
>>> -#ifdef CONFIG_NO_HZ_COMMON
>>>   /**
>>>    * vtime_reset - Fast forward vtime entry clocks
>>>    *
>>> @@ -394,6 +393,7 @@ void vtime_reset(void)
>>>   #endif
>>>   }
>>> +#ifdef CONFIG_NO_HZ_COMMON
>>>   /**
>>>    * vtime_dyntick_start - Inform vtime about entry to idle-dynticks
>>>    *
>>> @@ -933,6 +933,7 @@ static void __init set_decrementer_max(void)
>>>   static void __init init_decrementer_clockevent(void)
>>>   {
>>>       register_decrementer_clockevent(smp_processor_id());
>>> +    vtime_reset();
>>>   }
>>>   void secondary_cpu_time_init(void)
>>> @@ -948,6 +949,7 @@ void secondary_cpu_time_init(void)
>>>       /* FIME: Should make unrelated change to move snapshot_timebase
>>>        * call here ! */
>>>       register_decrementer_clockevent(smp_processor_id());
>>> +    vtime_reset();
>>>   }
>>>   /*
>>
> 

Sorry i should have put this earlier, But this applies on top of tip/timers/nohz
at 6199f9999a9b (origin/timers/nohz) sched/cputime: Handle dyntick-idle steal time correctly
(In case anyone tried applying on powerpc tree, it would fail)