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