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

[Anton Blanchard]

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?

Anton