On Fri, 21 Sep 2012, Paul E. McKenney wrote: > Could you please point me to a recipe for creating a minimal userspace? > Just in case it is the userspac erather than the architecture/hardware > that makes the difference. Tony's suggestion is pretty good. Note that there may also be differences in kernel timers -- either between x86 and ARM architectures, or loaded device drivers -- that may confound the problem. > Just to make sure I understand the combinations: > > o All stalls have happened when running a minimal userspace. > o CONFIG_NO_HZ=n suppresses the stalls. > o CONFIG_RCU_FAST_NO_HZ (which depends on CONFIG_NO_HZ=y) has > no observable effect on the stalls. > > Did I get that right, or am I missing a combination? That's correct. > Indeed, rcu_idle_gp_timer_func() is a bit strange in that it is > cancelled upon exit from idle, and therefore should (almost) never > actually execute. Its sole purpose is to wake up the CPU. ;-) Right. Just curious, what would wake up the kernel from idle to handle a grace period expiration when CONFIG_RCU_FAST_NO_HZ=n? On a very idle system, the time between timer ticks could potentially be several tens of seconds. - Paul -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
