From: "Christophe Leroy (CS GROUP)" <chleroy@kernel•org>
To: Shrikanth Hegde <sshegde@linux•ibm.com>,
maddy@linux•ibm.com, linuxppc-dev@lists•ozlabs.org
Cc: frederic@kernel•org
Subject: Re: [PATCH] powerpc/vtime: Initialize starttime at boot for native accounting
Date: Fri, 5 Jun 2026 07:32:56 +0200 [thread overview]
Message-ID: <b9019b74-57ff-47ed-9215-c6bdca98b2ce@kernel.org> (raw)
In-Reply-To: <d56bebd8-bd0e-4e3d-b44f-6c2ca27ab5a9@linux.ibm.com>
Hi Shrikanth,
Le 05/06/2026 à 05:03, Shrikanth Hegde a écrit :
> 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.
Even if automatic backport will fail, it shouldn't be difficult to
perform a manual backport by just adding the missing vtime_reset().
So I would put the Fixes tag to make people award.
>
>
>>
>>>
>>>>
>>>> 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)
Yep, I first looked vtime_reset() into linus tree, then found it in
linux-next.
Christophe
prev parent reply other threads:[~2026-06-05 5:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-04 13:24 [PATCH] powerpc/vtime: Initialize starttime at boot for native accounting Shrikanth Hegde
2026-06-04 14:51 ` Christophe Leroy (CS GROUP)
2026-06-04 15:12 ` Christophe Leroy (CS GROUP)
2026-06-05 3:03 ` Shrikanth Hegde
2026-06-05 5:32 ` Christophe Leroy (CS GROUP) [this message]
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