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* [PATCH 2/2] x86: Move x86_cpu_to_apicid to the __read_mostly section
@ 2012-04-17 11:16 Vlad Zolotarov
  0 siblings, 0 replies; 5+ messages in thread
From: Vlad Zolotarov @ 2012-04-17 11:16 UTC (permalink / raw)
  To: linux-kernel, Thomas Gleixner, Ingo Molnar, H. Peter Anvin
  Cc: Shai Fultheim (Shai@ScaleMP.com), ido

From: Shai Fultheim <shai@scalemp.com>

x86_cpu_to_apicid is only written to during initialization. Benchmarks
show that moving it to the __read_mostly section helps avoid false
sharing on large multiprocessing systems.

Signed-off-by: Shai Fultheim <shai@scalemp.com>
Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>
---
 arch/x86/include/asm/smp.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 0434c40..b9d6c1e 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -53,7 +53,7 @@ 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_READ_MOSTLY(u16, x86_cpu_to_apicid);
 DECLARE_EARLY_PER_CPU(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);
-- 
1.7.7.6


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] x86: Move x86_cpu_to_apicid to the __read_mostly section
  2012-05-07 13:41   ` Vlad Zolotarov
@ 2012-05-07 14:07     ` Ingo Molnar
  0 siblings, 0 replies; 5+ messages in thread
From: Ingo Molnar @ 2012-05-07 14:07 UTC (permalink / raw)
  To: Vlad Zolotarov
  Cc: linux-kernel, alan, Shai Fultheim (Shai@ScaleMP.com),
	H. Peter Anvin, Thomas Gleixner, Ingo Molnar


* Vlad Zolotarov <vlad@scalemp.com> wrote:

> On Monday, May 07, 2012 01:52:47 pm Ingo Molnar wrote:
> > * Vlad Zolotarov <vlad@scalemp.com> wrote:
> > > From: Shai Fultheim <shai@scalemp.com>
> > > 
> > > x86_cpu_to_apicid is only written to during initialization. Benchmarks
> > > show that moving it to the __read_mostly section helps avoid false
> > > sharing on large multiprocessing systems.
> > > 
> > > Signed-off-by: Shai Fultheim <shai@scalemp.com>
> > > Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>
> > > ---
> > > 
> > >  arch/x86/include/asm/smp.h |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> > > index 0434c40..b9d6c1e 100644
> > > --- a/arch/x86/include/asm/smp.h
> > > +++ b/arch/x86/include/asm/smp.h
> > > @@ -53,7 +53,7 @@ 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_READ_MOSTLY(u16, x86_cpu_to_apicid);
> > > 
> > >  DECLARE_EARLY_PER_CPU(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);
> > 
> > Looks like all of the surrounding fields are read mostly as
> > well, only initialized very rarely, during cpu init?
> 
> U r right. At least x86_bios_cpu_apicid is read mostly as 
> well. I'll fix and respin.

Thanks.

> Did u have a chance to look at the other "__read_mostly" patch for fs/buffer.c 
> I've sent?

Haven't been involved with fs/buffer.c for some time, please 
send it to the relevant maintainer:

 $ scripts/get_maintainer.pl -f fs/buffer.c 
 Alexander Viro <viro@zeniv.linux.org.uk> (maintainer:FILESYSTEMS (VFS...)
 linux-fsdevel@vger.kernel.org (open list:FILESYSTEMS (VFS...)
 linux-kernel@vger.kernel.org (open list)

Thanks,

	Ingo

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] x86: Move x86_cpu_to_apicid to the __read_mostly section
  2012-05-07 10:52 ` Ingo Molnar
@ 2012-05-07 13:41   ` Vlad Zolotarov
  2012-05-07 14:07     ` Ingo Molnar
  0 siblings, 1 reply; 5+ messages in thread
From: Vlad Zolotarov @ 2012-05-07 13:41 UTC (permalink / raw)
  To: Ingo Molnar
  Cc: linux-kernel, alan, Shai Fultheim (Shai@ScaleMP.com),
	H. Peter Anvin, Thomas Gleixner, Ingo Molnar

On Monday, May 07, 2012 01:52:47 pm Ingo Molnar wrote:
> * Vlad Zolotarov <vlad@scalemp.com> wrote:
> > From: Shai Fultheim <shai@scalemp.com>
> > 
> > x86_cpu_to_apicid is only written to during initialization. Benchmarks
> > show that moving it to the __read_mostly section helps avoid false
> > sharing on large multiprocessing systems.
> > 
> > Signed-off-by: Shai Fultheim <shai@scalemp.com>
> > Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>
> > ---
> > 
> >  arch/x86/include/asm/smp.h |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> > index 0434c40..b9d6c1e 100644
> > --- a/arch/x86/include/asm/smp.h
> > +++ b/arch/x86/include/asm/smp.h
> > @@ -53,7 +53,7 @@ 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_READ_MOSTLY(u16, x86_cpu_to_apicid);
> > 
> >  DECLARE_EARLY_PER_CPU(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);
> 
> Looks like all of the surrounding fields are read mostly as
> well, only initialized very rarely, during cpu init?

U r right. At least x86_bios_cpu_apicid is read mostly as well. I'll fix and 
respin.

Did u have a chance to look at the other "__read_mostly" patch for fs/buffer.c 
I've sent?

thanks,
vlad

> 
> Thanks,
> 
> 	Ingo
> --
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^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] x86: Move x86_cpu_to_apicid to the __read_mostly section
  2012-04-24 11:29 Vlad Zolotarov
@ 2012-05-07 10:52 ` Ingo Molnar
  2012-05-07 13:41   ` Vlad Zolotarov
  0 siblings, 1 reply; 5+ messages in thread
From: Ingo Molnar @ 2012-05-07 10:52 UTC (permalink / raw)
  To: Vlad Zolotarov
  Cc: linux-kernel, alan, Shai Fultheim (Shai@ScaleMP.com),
	H. Peter Anvin, Thomas Gleixner, Ingo Molnar


* Vlad Zolotarov <vlad@scalemp.com> wrote:

> From: Shai Fultheim <shai@scalemp.com>
> 
> x86_cpu_to_apicid is only written to during initialization. Benchmarks
> show that moving it to the __read_mostly section helps avoid false
> sharing on large multiprocessing systems.
> 
> Signed-off-by: Shai Fultheim <shai@scalemp.com>
> Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>
> ---
>  arch/x86/include/asm/smp.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 0434c40..b9d6c1e 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -53,7 +53,7 @@ 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_READ_MOSTLY(u16, x86_cpu_to_apicid);
>  DECLARE_EARLY_PER_CPU(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);

Looks like all of the surrounding fields are read mostly as 
well, only initialized very rarely, during cpu init?

Thanks,

	Ingo

^ permalink raw reply	[flat|nested] 5+ messages in thread
* [PATCH 2/2] x86: Move x86_cpu_to_apicid to the __read_mostly section
@ 2012-04-24 11:29 Vlad Zolotarov
  2012-05-07 10:52 ` Ingo Molnar
  0 siblings, 1 reply; 5+ messages in thread
From: Vlad Zolotarov @ 2012-04-24 11:29 UTC (permalink / raw)
  To: linux-kernel
  Cc: alan, Shai Fultheim (Shai@ScaleMP.com),
	H. Peter Anvin, Thomas Gleixner, Ingo Molnar

From: Shai Fultheim <shai@scalemp.com>

x86_cpu_to_apicid is only written to during initialization. Benchmarks
show that moving it to the __read_mostly section helps avoid false
sharing on large multiprocessing systems.

Signed-off-by: Shai Fultheim <shai@scalemp.com>
Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>
---
 arch/x86/include/asm/smp.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 0434c40..b9d6c1e 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -53,7 +53,7 @@ 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_READ_MOSTLY(u16, x86_cpu_to_apicid);
 DECLARE_EARLY_PER_CPU(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);
-- 
1.7.7.6


^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2012-05-07 14:07 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2012-04-17 11:16 [PATCH 2/2] x86: Move x86_cpu_to_apicid to the __read_mostly section Vlad Zolotarov
2012-04-24 11:29 Vlad Zolotarov
2012-05-07 10:52 ` Ingo Molnar
2012-05-07 13:41   ` Vlad Zolotarov
2012-05-07 14:07     ` Ingo Molnar

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