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author | Vlad Zolotarov <vlad@scalemp.com> | 2012-06-11 09:56:52 (GMT) |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2012-06-14 10:42:11 (GMT) |
commit | 0816b0f0365539c8f6280634d2c1778d0108d8f5 (patch) | |
tree | 92ee18c8ca0475e636558a36572f28d62bcc627d /arch/x86/include | |
parent | c35f77417ebfc7c21c02aa9c8c30aa4cecf331d6 (diff) | |
download | linux-fsl-qoriq-0816b0f0365539c8f6280634d2c1778d0108d8f5.tar.xz |
x86: Add read_mostly declaration/definition to variables from smp.h
Add "read-mostly" qualifier to the following variables in
smp.h:
- cpu_sibling_map
- cpu_core_map
- cpu_llc_shared_map
- cpu_llc_id
- cpu_number
- x86_cpu_to_apicid
- x86_bios_cpu_apicid
- x86_cpu_to_logical_apicid
As long as all the variables above are only written during the
initialization, this change is meant to prevent the false
sharing. More specifically, on vSMP Foundation platform
x86_cpu_to_apicid shared the same internode_cache_line with
frequently written lapic_events.
From the analysis of the first 33 per_cpu variables out of 219
(memories they describe, to be more specific) the 8 have read_mostly
nature (tlb_vector_offset, cpu_loops_per_jiffy, xen_debug_irq, etc.)
and 25 are frequently written (irq_stack_union, gdt_page,
exception_stacks, idt_desc, etc.).
Assuming that the spread of the rest of the per_cpu variables is
similar, identifying the read mostly memories will make more sense
in terms of long-term code maintenance comparing to identifying
frequently written memories.
Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>
Acked-by: Shai Fultheim <shai@scalemp.com>
Cc: Shai Fultheim (Shai@ScaleMP.com) <Shai@scalemp.com>
Cc: ido@wizery.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1719258.EYKzE4Zbq5@vlad
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include')
-rw-r--r-- | arch/x86/include/asm/apic.h | 2 | ||||
-rw-r--r-- | arch/x86/include/asm/smp.h | 16 |
2 files changed, 9 insertions, 9 deletions
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index eaff479..a907d4d 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -537,7 +537,7 @@ static inline const struct cpumask *default_target_cpus(void) #endif } -DECLARE_EARLY_PER_CPU(u16, x86_bios_cpu_apicid); +DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_bios_cpu_apicid); static inline unsigned int read_apic_id(void) diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index f483945..cc1df2b 100644 --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -31,12 +31,12 @@ static inline bool cpu_has_ht_siblings(void) return has_siblings; } -DECLARE_PER_CPU(cpumask_var_t, cpu_sibling_map); -DECLARE_PER_CPU(cpumask_var_t, cpu_core_map); +DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_map); +DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_map); /* cpus sharing the last level cache: */ -DECLARE_PER_CPU(cpumask_var_t, cpu_llc_shared_map); -DECLARE_PER_CPU(u16, cpu_llc_id); -DECLARE_PER_CPU(int, cpu_number); +DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map); +DECLARE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id); +DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number); static inline struct cpumask *cpu_sibling_mask(int cpu) { @@ -53,10 +53,10 @@ static inline struct cpumask *cpu_llc_shared_mask(int cpu) return per_cpu(cpu_llc_shared_map, cpu); } -DECLARE_EARLY_PER_CPU(u16, x86_cpu_to_apicid); -DECLARE_EARLY_PER_CPU(u16, x86_bios_cpu_apicid); +DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_cpu_to_apicid); +DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_bios_cpu_apicid); #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_32) -DECLARE_EARLY_PER_CPU(int, x86_cpu_to_logical_apicid); +DECLARE_EARLY_PER_CPU_READ_MOSTLY(int, x86_cpu_to_logical_apicid); #endif /* Static state in head.S used to set up a CPU */ |