Messages in this thread | | | Date | Mon, 1 Dec 2008 08:44:47 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] Don't export sched_mc_power_savings in laptops |
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* Mahesh Jagannath Salgaonkar <mahesh@linux.vnet.ibm.com> wrote:
> Ingo Molnar wrote: >> * Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com> wrote: >> >> >>> Fix to prevent sched_mc_power_saving from being exported through sysfs >>> for multicore single socket (Laptop). >>> CPU core map of the boot cpu should be equal to possible >>> number >>> of cpus for single socket system. >>> This fix has been developed at FOSS.in kernel workout. >>> Signed-off-by: Mahesh Salgaonkar >>> <mahesh@linux.vnet.ibm.com> >>> >>> diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h >>> index 4850e4b..4adc830 100644 >>> --- a/arch/x86/include/asm/topology.h >>> +++ b/arch/x86/include/asm/topology.h >>> @@ -239,7 +239,7 @@ struct pci_bus; >>> void set_pci_bus_resources_arch_default(struct pci_bus *b); >>> #ifdef CONFIG_SMP >>> -#define mc_capable() (boot_cpu_data.x86_max_cores > 1) >>> +#define mc_capable() (cpus_weight(per_cpu(cpu_core_map,0)) != nr_cpu_ids) >>> >> >> hm, dunno. sched_mc_power_savings should have no effect on >> single-socket systems, right? So the knob should have no effect. >> >> Ingo >> > Hi Ingo, > > Yes, it will not have any effect but it enables additional code path > leading to an overhead in case of single-socket system. This overhead > is only if "sched_mc_power_savings = 1", however we are still leaving > it to zero (default) and preventing user space from turning it on by > mistake.
okay, makes sense - i've applied it to tip/sched/urgent (for v2.6.28 merge), thanks Mahesh!
Ingo
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