Messages in this thread | | | Date | Mon, 01 Dec 2008 12:20:27 +0530 | From | Mahesh Jagannath Salgaonkar <> | Subject | Re: [PATCH] Don't export sched_mc_power_savings in laptops |
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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.
Thanks, -Mahesh.
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