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This patch has been superseded by Nick's patch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-npig...@gmail.com/
Christophe
