Messages in this thread | | | Date | Tue, 25 Oct 2011 23:21:43 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH] APICID: Avoid false sharing on the read mostly x86_cpu_to_apicid |
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On Tue, 25 Oct 2011, Eial Czerwacki wrote:
> Avoid false sharing on the read mostly x86_cpu_to_apicid by moving it to > __read_mostly section.
x86_cpu_to_apicid used to be in .init.data and now it's never freed after boot?
> The per-cpu area is write and read and this symbol shows up high on ipi > intensive/x86_cpu_to_apicid load. > > Signed-off-by: Eial Czerwacki<eial@scalemp.com> > Signed-off-by: Shai Fultheim<shai@scalemp.com> > Author: Ravikiran Thirumalai<kiran@scalex86.org>
If the author isn't you, then the patch should start with a single line that says "From: name <email>" of the author followed by a blank line. It's also strange that the author doesn't have a sign-off line.
Your email client also has corrupted the inline patch, please see Documentation/email-clients.txt.
And, finally, please send this to the x86 maintainers once fixed. See ./scripts/get_maintainers.pl <your patch>.
> Index: b/arch/x86/include/asm/smp.h > =================================================================== > --- a/arch/x86/include/asm/smp.h 2010-06-01 09:56:03.000000000 -0700 > +++ b/arch/x86/include/asm/smp.h 2010-06-02 15:59:21.000000000 -0700 > @@ -36,7 +36,8 @@ static inline struct cpumask *cpu_core_m > return per_cpu(cpu_core_map, cpu); > } > > -DECLARE_EARLY_PER_CPU(u16, x86_cpu_to_apicid); > +extern u16 x86_cpu_to_apicid[NR_CPUS]; > + > DECLARE_EARLY_PER_CPU(u16, x86_bios_cpu_apicid); > > /* Static state in head.S used to set up a CPU */ > @@ -142,7 +143,7 @@ void native_send_call_func_ipi(const str > void native_send_call_func_single_ipi(int cpu); > > void smp_store_cpu_info(int id); > -#define cpu_physical_id(cpu) per_cpu(x86_cpu_to_apicid, cpu) > +#define cpu_physical_id(cpu) x86_cpu_to_apicid[cpu] > > /* We don't mark CPUs online until __cpu_up(), so we need another measure */ > static inline int num_booting_cpus(void) > Index: b/arch/x86/kernel/acpi/boot.c > =================================================================== > --- a/arch/x86/kernel/acpi/boot.c 2010-06-01 09:56:03.000000000 -0700 > +++ b/arch/x86/kernel/acpi/boot.c 2010-06-02 15:59:21.000000000 -0700 > @@ -568,7 +568,7 @@ EXPORT_SYMBOL(acpi_map_lsapic); > > int acpi_unmap_lsapic(int cpu) > { > - per_cpu(x86_cpu_to_apicid, cpu) = -1; > + x86_cpu_to_apicid[cpu] = -1; > set_cpu_present(cpu, false); > num_processors--; >
Shouldn't this be BAD_APICID? Not sure where we check for -1.
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