x86: Added read_mostly declaration/definition to vars from smp.h

PATCH Superseded Vlad Zolotarov 2 participants 3 messages May 15, 2012 – May 20, 2012 x86

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Vlad Zolotarov

author

2012-05-15 15:32 UTC #0 lore raw

PATCH v2 2/2 x86: Added read_mostly declaration/definition to vars from smp.h

Added a "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 and improve the performance on large multiprocessor systems.

Signed-off-by Vlad Zolotarov <[email protected]>

Signed-off-by Shai Fultheim <[email protected]>

---
 arch/x86/include/asm/apic.h    |    2 +-
 arch/x86/include/asm/smp.h     |   16 ++++++++--------
 arch/x86/kernel/apic/apic.c    |    6 +++---
 arch/x86/kernel/setup_percpu.c |    2 +-
 arch/x86/kernel/smpboot.c      |    8 ++++----
 5 files changed, 17 insertions(+), 17 deletions(-)

arch/x86/include/asm/apic.h +1 -1

index d854101..ca11940 100644
@@ -520,7 +520,7 @@ 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)

arch/x86/include/asm/smp.h +8 -8

index 0434c40..2a5304a 100644
@@ -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 */

arch/x86/kernel/apic/apic.c +3 -3

index edc2448..33c3672 100644
@@ -74,8 +74,8 @@ physid_mask_t phys_cpu_present_map;
 /*
  * Map cpu index to physical APIC ID
  */
-DEFINE_EARLY_PER_CPU(u16, x86_cpu_to_apicid, BAD_APICID);
-DEFINE_EARLY_PER_CPU(u16, x86_bios_cpu_apicid, BAD_APICID);
+DEFINE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_cpu_to_apicid, BAD_APICID);
+DEFINE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_bios_cpu_apicid, BAD_APICID);
 EXPORT_EARLY_PER_CPU_SYMBOL(x86_cpu_to_apicid);
 EXPORT_EARLY_PER_CPU_SYMBOL(x86_bios_cpu_apicid);

@@ -87,7 +87,7 @@ EXPORT_EARLY_PER_CPU_SYMBOL(x86_bios_cpu_apicid);
  * used for the mapping.  This is where the behaviors of x86_64 and 32
  * actually diverge.  Let's keep it ugly for now.
  */
-DEFINE_EARLY_PER_CPU(int, x86_cpu_to_logical_apicid, BAD_APICID);
+DEFINE_EARLY_PER_CPU_READ_MOSTLY(int, x86_cpu_to_logical_apicid, BAD_APICID);
 
 /*
  * Knob to control our willingness to enable the local APIC.

arch/x86/kernel/setup_percpu.c +1 -1

index 5a98aa2..5cdff03 100644
@@ -21,7 +21,7 @@
 #include <asm/cpu.h>
 #include <asm/stackprotector.h>
 
-DEFINE_PER_CPU(int, cpu_number);
+DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number);
 EXPORT_PER_CPU_SYMBOL(cpu_number);
 
 #ifdef CONFIG_X86_64

arch/x86/kernel/smpboot.c +4 -4

index 6e1e406..3d877b1 100644
@@ -118,17 +118,17 @@ int smp_num_siblings = 1;
 EXPORT_SYMBOL(smp_num_siblings);
 
 /* Last level cache ID of each logical CPU */
-DEFINE_PER_CPU(u16, cpu_llc_id) = BAD_APICID;
+DEFINE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id) = BAD_APICID;
 
 /* representing HT siblings of each logical CPU */
-DEFINE_PER_CPU(cpumask_var_t, cpu_sibling_map);
+DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_map);
 EXPORT_PER_CPU_SYMBOL(cpu_sibling_map);
 
 /* representing HT and core siblings of each logical CPU */
-DEFINE_PER_CPU(cpumask_var_t, cpu_core_map);
+DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_map);
 EXPORT_PER_CPU_SYMBOL(cpu_core_map);
 
-DEFINE_PER_CPU(cpumask_var_t, cpu_llc_shared_map);
+DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map);
 
 /* Per CPU bogomips and other parameters */
 DEFINE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info);

Signature · 1 line

1.7.0.4

Ingo Molnar

2012-05-18 08:14 UTC #1 lore raw

Quoted 16 lines · Vlad Zolotarov

Added a "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 and improve the performance on large multiprocessor systems.
Signed-off-by Vlad Zolotarov <[email protected]>
Signed-off-by Shai Fultheim <[email protected]>

Quoted 7 lines

---
 arch/x86/include/asm/apic.h    |    2 +-
 arch/x86/include/asm/smp.h     |   16 ++++++++--------
 arch/x86/kernel/apic/apic.c    |    6 +++---
 arch/x86/kernel/setup_percpu.c |    2 +-
 arch/x86/kernel/smpboot.c      |    8 ++++----
 5 files changed, 17 insertions(+), 17 deletions(-)

This does not build on !SMP kernels that has APIC enabled.

Thanks,

Ingo

Vlad

author

2012-05-20 13:55 UTC #2 lore raw

Quoted 26 lines · Ingo Molnar

Quoted 16 lines · Vlad Zolotarov
Added a "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 and improve the performance on large multiprocessor systems.
Signed-off-by Vlad Zolotarov<[email protected]>
Signed-off-by Shai Fultheim<[email protected]>
Quoted 7 lines
---
  arch/x86/include/asm/apic.h    |    2 +-
  arch/x86/include/asm/smp.h     |   16 ++++++++--------
  arch/x86/kernel/apic/apic.c    |    6 +++---
  arch/x86/kernel/setup_percpu.c |    2 +-
  arch/x86/kernel/smpboot.c      |    8 ++++----
  5 files changed, 17 insertions(+), 17 deletions(-)

Quoted 1 line

This does not build on !SMP kernels that has APIC enabled.

Oops... :) My bad. I'll rebase and respin.

Thanks,
vlad

Quoted 10 lines

Thanks,
Ingo
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