Messages in this thread | | | Date | Tue, 25 Aug 2009 15:04:42 +0530 | From | Gautham R Shenoy <> | Subject | Re: [PATCH 9/15] sched: Check sched_mn_power_savings when setting flags for CPU and MN domains |
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On Mon, Aug 24, 2009 at 04:57:42PM +0200, Peter Zijlstra wrote: > On Thu, 2009-08-20 at 15:40 +0200, Andreas Herrmann wrote: > > Use new function sd_balance_for_mn_power() and adapt > > sd_balance_for_package_power() and sd_power_saving_flags() for correct > > setting of flags SD_POWERSAVINGS_BALANCE and SD_BALANCE_NEWIDLE in CPU > > and MN domains. > > > > Furthermore add flag SD_SHARE_PKG_RESOURCES to MN domain. > > Rational: a multi-node processor most likely shares package resources > > (on Magny-Cours the package constitues a "voltage domain"). > > IIRC SD_SHARE_PKG_RESOURCES plays games with the cpu_pwer of a > sched_domain, which breaks in all kinds of curious ways, this adds more > breakage afaict. > > ego?
A domain which has SD_SHARE_PKG_RESOURCES, will always have the __cpu_power = SD_LOAD_SCALE if the domain hasn't set SD_POWERSAVINGS_BALANCE flag.
The problem which you are talking about is when you offline a CPU of such a domain, it will still show the same cpu_power, which can confuse the scheduler.
Eg: A Dual socket Dual core machine, in the absense of SD_POWERSAVINGS_BALANCE the SD_LV_CPU which has SD_SHARE_PKG_RESOURCES set will have both of it's group->cpu_power set to SD_LOAD_SCALE. If we offline, say one of the four cores, the group->cpu_power the corresponding group will will still be SD_LOAD_SCALE.
This might affect the fairness calculations. For eg, if you have 6 tasks running, the ideal placement should have been 4 on the socket whose CPUs are online and 2 on which one of the cpus has been offlined. But in this case, we will have 3 + 3, which is not correct.
> > > Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com> > > --- > > arch/x86/include/asm/topology.h | 3 ++- > > include/linux/sched.h | 14 ++++++++++++-- > > 2 files changed, 14 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h > > index 6d7d133..4a520b8 100644 > > --- a/arch/x86/include/asm/topology.h > > +++ b/arch/x86/include/asm/topology.h > > @@ -198,7 +198,8 @@ static inline void setup_node_to_cpumask_map(void) { } > > | SD_BALANCE_EXEC \ > > | SD_WAKE_AFFINE \ > > | SD_WAKE_BALANCE \ > > - | sd_balance_for_package_power()\ > > + | SD_SHARE_PKG_RESOURCES\ > > + | sd_balance_for_mn_power()\ > > | sd_power_saving_flags(),\ > > .last_balance = jiffies, \ > > .balance_interval = 1, \ > > diff --git a/include/linux/sched.h b/include/linux/sched.h > > index 5755643..c53bdd8 100644 > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -844,9 +844,18 @@ static inline int sd_balance_for_mc_power(void) > > return 0; > > } > > > > +static inline int sd_balance_for_mn_power(void) > > +{ > > + if (sched_mc_power_savings || sched_smt_power_savings) > > + return SD_POWERSAVINGS_BALANCE; > > + > > + return 0; > > +} > > + > > static inline int sd_balance_for_package_power(void) > > { > > - if (sched_mc_power_savings | sched_smt_power_savings) > > + if (sched_mn_power_savings || sched_mc_power_savings || > > + sched_smt_power_savings) > > return SD_POWERSAVINGS_BALANCE; > > > > return 0; > > @@ -860,7 +869,8 @@ static inline int sd_balance_for_package_power(void) > > > > static inline int sd_power_saving_flags(void) > > { > > - if (sched_mc_power_savings | sched_smt_power_savings) > > + if (sched_mn_power_savings || sched_mc_power_savings || > > + sched_smt_power_savings) > > return SD_BALANCE_NEWIDLE; > > > > return 0;
-- Thanks and Regards gautham
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