On Mon, 22 May 2017 14:15:57 +1000 Michael Ellerman <m...@ellerman.id.au> wrote:
> Anton Blanchard <an...@ozlabs.org> writes: > > > From: Anton Blanchard <an...@samba.org> > > > > 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). Not ACCOUNT_CPU_USER_ENTRY/EXIT, which adds a fair cost to kernel entry/exit (my notes say ~70 cycles on getppid() out of 3-4 hundred). > > > 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. > > Doesn't dropping this mean we never count stolen time? > > cheers
