diff options
author | Vlad Zolotarov <vlad@scalemp.com> | 2012-06-11 05:56:52 -0400 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2012-06-14 06:42:11 -0400 |
commit | 0816b0f0365539c8f6280634d2c1778d0108d8f5 (patch) | |
tree | 92ee18c8ca0475e636558a36572f28d62bcc627d /arch/x86/include/asm/smp.h | |
parent | c35f77417ebfc7c21c02aa9c8c30aa4cecf331d6 (diff) |
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/asm/smp.h')
-rw-r--r-- | arch/x86/include/asm/smp.h | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index f48394513c37..cc1df2b5cc65 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) | |||
31 | return has_siblings; | 31 | return has_siblings; |
32 | } | 32 | } |
33 | 33 | ||
34 | DECLARE_PER_CPU(cpumask_var_t, cpu_sibling_map); | 34 | DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_map); |
35 | DECLARE_PER_CPU(cpumask_var_t, cpu_core_map); | 35 | DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_map); |
36 | /* cpus sharing the last level cache: */ | 36 | /* cpus sharing the last level cache: */ |
37 | DECLARE_PER_CPU(cpumask_var_t, cpu_llc_shared_map); | 37 | DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map); |
38 | DECLARE_PER_CPU(u16, cpu_llc_id); | 38 | DECLARE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id); |
39 | DECLARE_PER_CPU(int, cpu_number); | 39 | DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number); |
40 | 40 | ||
41 | static inline struct cpumask *cpu_sibling_mask(int cpu) | 41 | static inline struct cpumask *cpu_sibling_mask(int cpu) |
42 | { | 42 | { |
@@ -53,10 +53,10 @@ static inline struct cpumask *cpu_llc_shared_mask(int cpu) | |||
53 | return per_cpu(cpu_llc_shared_map, cpu); | 53 | return per_cpu(cpu_llc_shared_map, cpu); |
54 | } | 54 | } |
55 | 55 | ||
56 | DECLARE_EARLY_PER_CPU(u16, x86_cpu_to_apicid); | 56 | DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_cpu_to_apicid); |
57 | DECLARE_EARLY_PER_CPU(u16, x86_bios_cpu_apicid); | 57 | DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_bios_cpu_apicid); |
58 | #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_32) | 58 | #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_32) |
59 | DECLARE_EARLY_PER_CPU(int, x86_cpu_to_logical_apicid); | 59 | DECLARE_EARLY_PER_CPU_READ_MOSTLY(int, x86_cpu_to_logical_apicid); |
60 | #endif | 60 | #endif |
61 | 61 | ||
62 | /* Static state in head.S used to set up a CPU */ | 62 | /* Static state in head.S used to set up a CPU */ |