define new percpu interface for shared data

per cpu data section contains two types of data.  One set which is
exclusively accessed by the local cpu and the other set which is per cpu,
but also shared by remote cpus.  In the current kernel, these two sets are
not clearely separated out.  This can potentially cause the same data
cacheline shared between the two sets of data, which will result in
unnecessary bouncing of the cacheline between cpus.

One way to fix the problem is to cacheline align the remotely accessed per
cpu data, both at the beginning and at the end.  Because of the padding at
both ends, this will likely cause some memory wastage and also the
interface to achieve this is not clean.

This patch:

Moves the remotely accessed per cpu data (which is currently marked
as ____cacheline_aligned_in_smp) into a different section, where all the data
elements are cacheline aligned. And as such, this differentiates the local
only data and remotely accessed data cleanly.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: <linux-arch@vger.kernel.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

18 files changed, 25 insertions, 53 deletions

diff --git a/arch/alpha/kernel/vmlinux.lds.S b/arch/alpha/kernel/vmlinux.lds.S
index 449e76f118d..6f4f0378e70 100644
--- a/arch/alpha/kernel/vmlinux.lds.S
+++ b/arch/alpha/kernel/vmlinux.lds.S
@@ -69,10 +69,7 @@ SECTIONS
   . = ALIGN(8);
   SECURITY_INIT
 
-  . = ALIGN(8192);
-  __per_cpu_start = .;
-  .data.percpu : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(8192)
 
   . = ALIGN(2*8192);
   __init_end = .;
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 2b7a8f5d8cf..5ff5406666b 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -66,6 +66,7 @@ SECTIONS
 		. = ALIGN(4096);
 		__per_cpu_start = .;
 			*(.data.percpu)
+			*(.data.percpu.shared_aligned)
 		__per_cpu_end = .;
 #ifndef CONFIG_XIP_KERNEL
 		__init_begin = _stext;
diff --git a/arch/cris/arch-v32/vmlinux.lds.S b/arch/cris/arch-v32/vmlinux.lds.S
index dfa25e1542b..651a77f2ccc 100644
--- a/arch/cris/arch-v32/vmlinux.lds.S
+++ b/arch/cris/arch-v32/vmlinux.lds.S
@@ -91,10 +91,7 @@ SECTIONS
 	}
 	SECURITY_INIT
 
-	. =  ALIGN (8192);
-	__per_cpu_start = .;
-	.data.percpu  : { *(.data.percpu) }
-	__per_cpu_end = .;
+	PERCPU(8192)
 
 #ifdef CONFIG_BLK_DEV_INITRD
 	.init.ramfs : {
diff --git a/arch/frv/kernel/vmlinux.lds.S b/arch/frv/kernel/vmlinux.lds.S
index 481dc137464..3b71e0c8639 100644
--- a/arch/frv/kernel/vmlinux.lds.S
+++ b/arch/frv/kernel/vmlinux.lds.S
@@ -57,10 +57,7 @@ SECTIONS
   __alt_instructions_end = .;
  .altinstr_replacement : { *(.altinstr_replacement) }
 
-  . = ALIGN(4096);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(4096)
 
 #ifdef CONFIG_BLK_DEV_INITRD
   . = ALIGN(4096);
diff --git a/arch/i386/kernel/vmlinux.lds.S b/arch/i386/kernel/vmlinux.lds.S
index 00f1bc47d3a..4dc44b8007c 100644
--- a/arch/i386/kernel/vmlinux.lds.S
+++ b/arch/i386/kernel/vmlinux.lds.S
@@ -181,6 +181,7 @@ SECTIONS
   .data.percpu  : AT(ADDR(.data.percpu) - LOAD_OFFSET) {
 	__per_cpu_start = .;
 	*(.data.percpu)
+	*(.data.percpu.shared_aligned)
 	__per_cpu_end = .;
   }
   . = ALIGN(4096);
diff --git a/arch/ia64/kernel/vmlinux.lds.S b/arch/ia64/kernel/vmlinux.lds.S
index 5a65965c8b5..860f251d2fc 100644
--- a/arch/ia64/kernel/vmlinux.lds.S
+++ b/arch/ia64/kernel/vmlinux.lds.S
@@ -206,6 +206,7 @@ SECTIONS
 	{
 		__per_cpu_start = .;
 		*(.data.percpu)
+		*(.data.percpu.shared_aligned)
 		__per_cpu_end = .;
 	}
   . = __phys_per_cpu_start + PERCPU_PAGE_SIZE;	/* ensure percpu data fits
diff --git a/arch/m32r/kernel/vmlinux.lds.S b/arch/m32r/kernel/vmlinux.lds.S
index 4e2d5b9f0a9..942a8c7a441 100644
--- a/arch/m32r/kernel/vmlinux.lds.S
+++ b/arch/m32r/kernel/vmlinux.lds.S
@@ -110,10 +110,7 @@ SECTIONS
   __initramfs_end = .;
 #endif
 
-  . = ALIGN(4096);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(4096)
   . = ALIGN(4096);
   __init_end = .;
   /* freed after init ends here */
diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 9b9992cd562..bc9bae2a73f 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -119,10 +119,7 @@ SECTIONS
   .init.ramfs : { *(.init.ramfs) }
   __initramfs_end = .;
 #endif
-  . = ALIGN(_PAGE_SIZE);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(_PAGE_SIZE)
   . = ALIGN(_PAGE_SIZE);
   __init_end = .;
   /* freed after init ends here */
diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S
index 4d96ba4b984..d4e6a93c8d9 100644
--- a/arch/parisc/kernel/vmlinux.lds.S
+++ b/arch/parisc/kernel/vmlinux.lds.S
@@ -181,10 +181,9 @@ SECTIONS
   .init.ramfs : { *(.init.ramfs) }
   __initramfs_end = .;
 #endif
-  . = ALIGN(ASM_PAGE_SIZE);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+
+  PERCPU(ASM_PAGE_SIZE)
+
   . = ALIGN(ASM_PAGE_SIZE);
   __init_end = .;
   /* freed after init ends here */
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index ae4acd84143..39fda6e6aa4 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -144,6 +144,7 @@ SECTIONS
 	.data.percpu : {
 		__per_cpu_start = .;
 		*(.data.percpu)
+		*(.data.percpu.shared_aligned)
 		__per_cpu_end = .;
 	}
 
diff --git a/arch/ppc/kernel/vmlinux.lds.S b/arch/ppc/kernel/vmlinux.lds.S
index 19db8746ff1..c0aac3ff9e9 100644
--- a/arch/ppc/kernel/vmlinux.lds.S
+++ b/arch/ppc/kernel/vmlinux.lds.S
@@ -130,10 +130,7 @@ SECTIONS
   __ftr_fixup : { *(__ftr_fixup) }
   __stop___ftr_fixup = .;
 
-  . = ALIGN(4096);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(4096)
 
 #ifdef CONFIG_BLK_DEV_INITRD
   . = ALIGN(4096);
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 7158a804a5e..61ffd50fac4 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -107,10 +107,7 @@ SECTIONS
   . = ALIGN(2);
   __initramfs_end = .;
 #endif
-  . = ALIGN(4096);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(4096)
   . = ALIGN(4096);
   __init_end = .;
   /* freed after init ends here */
diff --git a/arch/sh/kernel/vmlinux.lds.S b/arch/sh/kernel/vmlinux.lds.S
index 0696402f446..5ba216180b3 100644
--- a/arch/sh/kernel/vmlinux.lds.S
+++ b/arch/sh/kernel/vmlinux.lds.S
@@ -60,10 +60,7 @@ SECTIONS
   . = ALIGN(PAGE_SIZE);
   __nosave_end = .;
 
-  . = ALIGN(PAGE_SIZE);
-  __per_cpu_start = .;
-  .data.percpu : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(PAGE_SIZE)
   .data.cacheline_aligned : { *(.data.cacheline_aligned) }
 
   _edata = .;			/* End of data section */
diff --git a/arch/sh64/kernel/vmlinux.lds.S b/arch/sh64/kernel/vmlinux.lds.S
index 02aea86c590..8ac9c7c5f84 100644
--- a/arch/sh64/kernel/vmlinux.lds.S
+++ b/arch/sh64/kernel/vmlinux.lds.S
@@ -87,7 +87,10 @@ SECTIONS
 
   . = ALIGN(PAGE_SIZE);
   __per_cpu_start = .;
-  .data.percpu : C_PHYS(.data.percpu) { *(.data.percpu) }
+  .data.percpu : C_PHYS(.data.percpu) {
+	*(.data.percpu)
+	*(.data.percpu.shared_aligned)
+  }
   __per_cpu_end = . ;
   .data.cacheline_aligned : C_PHYS(.data.cacheline_aligned) { *(.data.cacheline_aligned) }
 
diff --git a/arch/sparc/kernel/vmlinux.lds.S b/arch/sparc/kernel/vmlinux.lds.S
index f75a1b82278..47583887abc 100644
--- a/arch/sparc/kernel/vmlinux.lds.S
+++ b/arch/sparc/kernel/vmlinux.lds.S
@@ -65,10 +65,7 @@ SECTIONS
   __initramfs_end = .;
 #endif
 
-  . = ALIGN(4096);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(4096)
   . = ALIGN(4096);
   __init_end = .;
   . = ALIGN(32);
diff --git a/arch/sparc64/kernel/vmlinux.lds.S b/arch/sparc64/kernel/vmlinux.lds.S
index 3ad10f3027e..481861764de 100644
--- a/arch/sparc64/kernel/vmlinux.lds.S
+++ b/arch/sparc64/kernel/vmlinux.lds.S
@@ -90,10 +90,8 @@ SECTIONS
   __initramfs_end = .;
 #endif
 
-  . = ALIGN(PAGE_SIZE);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(PAGE_SIZE)
+
   . = ALIGN(PAGE_SIZE);
   __init_end = .;
   __bss_start = .;
diff --git a/arch/x86_64/kernel/vmlinux.lds.S b/arch/x86_64/kernel/vmlinux.lds.S
index dbccfda8364..22590690a8a 100644
--- a/arch/x86_64/kernel/vmlinux.lds.S
+++ b/arch/x86_64/kernel/vmlinux.lds.S
@@ -194,10 +194,8 @@ SECTIONS
   __initramfs_end = .;
 #endif
 
-  . = ALIGN(4096);
-  __per_cpu_start = .;
-  .data.percpu  : AT(ADDR(.data.percpu) - LOAD_OFFSET) { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(4096)
+
   . = ALIGN(4096);
   __init_end = .;
 
diff --git a/arch/xtensa/kernel/vmlinux.lds.S b/arch/xtensa/kernel/vmlinux.lds.S
index b0582c3c5f8..3e31512109f 100644
--- a/arch/xtensa/kernel/vmlinux.lds.S
+++ b/arch/xtensa/kernel/vmlinux.lds.S
@@ -190,10 +190,7 @@ SECTIONS
   __initramfs_end = .;
 #endif
 
-  . = ALIGN(4096);
-  __per_cpu_start = .;
-  .data.percpu  : { *(.data.percpu) }
-  __per_cpu_end = .;
+  PERCPU(4096)
 
 
   /* We need this dummy segment here */