[PATCH] powerpc/64: Use tick accounting by default

[Christophe Leroy]

Le 22/05/2017 à 07:13, Anton Blanchard a écrit :
> Hi Michael,
> 
>>> ppc64 is the only architecture that turns on
>>> VIRT_CPU_ACCOUNTING_NATIVE by default. The overhead of this option
>>> is extremely high - a context switch microbenchmark using
>>> sched_yield() is almost 20% slower.
>>
>> Running on what? It should all be nop'ed out unless you're on a
>> platform that needs it (SPLPAR).
> 
> POWERNV native. We don't nop out all the vtime_account_* gunk do we? It
> is all those functions that are a large part of the problem.
> 
>>> To get finer grained user/hardirq/softirq statitics, the
>>> IRQ_TIME_ACCOUNTING option can be used instead, which has much lower
>>> overhead.
>>
>> Can it? We don't select HAVE_IRQ_TIME_ACCOUNTING, so AFAICS it can't
>> be enabled.
> 
> I have a separate patch to enable it.
> 
>> Doesn't dropping this mean we never count stolen time?
> 
> Perhaps. Do we have any applications left that care?
> 

This patch has been superseded by Nick's patch 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220525081346.871535-1-npiggin@gmail.com/

Christophe