On 09/15/2014 12:29 PM, Michael Ellerman wrote: > On Fri, 2014-09-12 at 16:31 +0530, Preeti U Murthy wrote: >> Today the procfs interface /proc/sys/kernel/powersave-nap is used to control >> entry into deep idle states beyond snooze. Check for the value of this >> parameter before entering fastsleep. We already do this check for nap in >> power7_idle(). >> >> Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com> >> --- >> >> drivers/cpuidle/cpuidle-powernv.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/drivers/cpuidle/cpuidle-powernv.c >> b/drivers/cpuidle/cpuidle-powernv.c >> index a64be57..b8ba52e 100644 >> --- a/drivers/cpuidle/cpuidle-powernv.c >> +++ b/drivers/cpuidle/cpuidle-powernv.c >> @@ -69,6 +69,12 @@ static int fastsleep_loop(struct cpuidle_device *dev, >> unsigned long old_lpcr = mfspr(SPRN_LPCR); >> unsigned long new_lpcr; >> >> + /* >> + * Verify if snooze is the only valid cpuidle state >> + */ >> + if (!(powersave_nap > 0)) >> + return index; >> + >> if (unlikely(system_state < SYSTEM_RUNNING)) >> return index; > > Doesn't the above mean we are just going to keep trying to go into fastsleep > again and again? Or does the idle code work out that it didn't work based on > the fact that we didn't sleep for the right period?
Thats right. The idle code figures that its judgment to enter fastsleep was not correct and applies a correction factor to its future decisions . This correction factor is intended to influence the cpuidle governor's decision on choosing an idle state for the cpu based on the history of wakeups. Hence a shallower idle state will be chosen here on in the above circumstance. > > We were talking about getting rid of powersave_nap altogether, but I think we > decided we couldn't, I forget. Isn't this a helpful knob to disable cpuidle at runtime? Currently we check the value of powersave_nap before entering both nap and fastsleep. Regards Preeti U Murthy > > cheers > > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
