diff options
| author | Tejun Heo <tj@kernel.org> | 2011-01-25 14:26:50 +0100 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2011-01-25 14:26:50 +0100 |
| commit | 19df0c2fef010e94e90df514aaf4e73f6b80145c (patch) | |
| tree | 4b0b9c10622aead0d8b658cca6c49090149a91a8 /include/asm-generic | |
| parent | c723fdab8aa728dc2bf0da6a0de8bb9c3f588d84 (diff) | |
percpu: align percpu readmostly subsection to cacheline
Currently percpu readmostly subsection may share cachelines with other
percpu subsections which may result in unnecessary cacheline bounce
and performance degradation.
This patch adds @cacheline parameter to PERCPU() and PERCPU_VADDR()
linker macros, makes each arch linker scripts specify its cacheline
size and use it to align percpu subsections.
This is based on Shaohua's x86 only patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Shaohua Li <shaohua.li@intel.com>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/vmlinux.lds.h | 35 |
1 files changed, 22 insertions, 13 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 6ebb81030d2..439df587c12 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -15,7 +15,7 @@ * HEAD_TEXT_SECTION * INIT_TEXT_SECTION(PAGE_SIZE) * INIT_DATA_SECTION(...) - * PERCPU(PAGE_SIZE) + * PERCPU(CACHELINE_SIZE, PAGE_SIZE) * __init_end = .; * * _stext = .; @@ -683,13 +683,18 @@ /** * PERCPU_VADDR - define output section for percpu area + * @cacheline: cacheline size * @vaddr: explicit base address (optional) * @phdr: destination PHDR (optional) * - * Macro which expands to output section for percpu area. If @vaddr - * is not blank, it specifies explicit base address and all percpu - * symbols will be offset from the given address. If blank, @vaddr - * always equals @laddr + LOAD_OFFSET. + * Macro which expands to output section for percpu area. + * + * @cacheline is used to align subsections to avoid false cacheline + * sharing between subsections for different purposes. + * + * If @vaddr is not blank, it specifies explicit base address and all + * percpu symbols will be offset from the given address. If blank, + * @vaddr always equals @laddr + LOAD_OFFSET. * * @phdr defines the output PHDR to use if not blank. Be warned that * output PHDR is sticky. If @phdr is specified, the next output @@ -700,7 +705,7 @@ * If there is no need to put the percpu section at a predetermined * address, use PERCPU(). */ -#define PERCPU_VADDR(vaddr, phdr) \ +#define PERCPU_VADDR(cacheline, vaddr, phdr) \ VMLINUX_SYMBOL(__per_cpu_load) = .; \ .data..percpu vaddr : AT(VMLINUX_SYMBOL(__per_cpu_load) \ - LOAD_OFFSET) { \ @@ -708,7 +713,9 @@ *(.data..percpu..first) \ . = ALIGN(PAGE_SIZE); \ *(.data..percpu..page_aligned) \ + . = ALIGN(cacheline); \ *(.data..percpu..readmostly) \ + . = ALIGN(cacheline); \ *(.data..percpu) \ *(.data..percpu..shared_aligned) \ VMLINUX_SYMBOL(__per_cpu_end) = .; \ @@ -717,18 +724,18 @@ /** * PERCPU - define output section for percpu area, simple version + * @cacheline: cacheline size * @align: required alignment * - * Align to @align and outputs output section for percpu area. This - * macro doesn't maniuplate @vaddr or @phdr and __per_cpu_load and + * Align to @align and outputs output section for percpu area. This macro + * doesn't manipulate @vaddr or @phdr and __per_cpu_load and * __per_cpu_start will be identical. * - * This macro is equivalent to ALIGN(align); PERCPU_VADDR( , ) except - * that __per_cpu_load is defined as a relative symbol against - * .data..percpu which is required for relocatable x86_32 - * configuration. + * This macro is equivalent to ALIGN(@align); PERCPU_VADDR(@cacheline,,) + * except that __per_cpu_load is defined as a relative symbol against + * .data..percpu which is required for relocatable x86_32 configuration. */ -#define PERCPU(align) \ +#define PERCPU(cacheline, align) \ . = ALIGN(align); \ .data..percpu : AT(ADDR(.data..percpu) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__per_cpu_load) = .; \ @@ -736,7 +743,9 @@ *(.data..percpu..first) \ . = ALIGN(PAGE_SIZE); \ *(.data..percpu..page_aligned) \ + . = ALIGN(cacheline); \ *(.data..percpu..readmostly) \ + . = ALIGN(cacheline); \ *(.data..percpu) \ *(.data..percpu..shared_aligned) \ VMLINUX_SYMBOL(__per_cpu_end) = .; \ |