5fb7dc37dc
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>
154 lines
4.3 KiB
C
154 lines
4.3 KiB
C
#ifndef __ARCH_I386_PERCPU__
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#define __ARCH_I386_PERCPU__
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#ifdef __ASSEMBLY__
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/*
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* PER_CPU finds an address of a per-cpu variable.
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*
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* Args:
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* var - variable name
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* reg - 32bit register
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*
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* The resulting address is stored in the "reg" argument.
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*
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* Example:
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* PER_CPU(cpu_gdt_descr, %ebx)
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*/
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#ifdef CONFIG_SMP
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#define PER_CPU(var, reg) \
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movl %fs:per_cpu__##this_cpu_off, reg; \
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lea per_cpu__##var(reg), reg
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#define PER_CPU_VAR(var) %fs:per_cpu__##var
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#else /* ! SMP */
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#define PER_CPU(var, reg) \
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movl $per_cpu__##var, reg
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#define PER_CPU_VAR(var) per_cpu__##var
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#endif /* SMP */
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#else /* ...!ASSEMBLY */
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/*
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* PER_CPU finds an address of a per-cpu variable.
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*
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* Args:
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* var - variable name
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* cpu - 32bit register containing the current CPU number
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*
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* The resulting address is stored in the "cpu" argument.
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*
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* Example:
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* PER_CPU(cpu_gdt_descr, %ebx)
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*/
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#ifdef CONFIG_SMP
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/* Same as generic implementation except for optimized local access. */
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#define __GENERIC_PER_CPU
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/* This is used for other cpus to find our section. */
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extern unsigned long __per_cpu_offset[];
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#define per_cpu_offset(x) (__per_cpu_offset[x])
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/* Separate out the type, so (int[3], foo) works. */
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#define DECLARE_PER_CPU(type, name) extern __typeof__(type) per_cpu__##name
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#define DEFINE_PER_CPU(type, name) \
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__attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name
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#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
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__attribute__((__section__(".data.percpu.shared_aligned"))) \
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__typeof__(type) per_cpu__##name \
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____cacheline_aligned_in_smp
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/* We can use this directly for local CPU (faster). */
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DECLARE_PER_CPU(unsigned long, this_cpu_off);
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/* var is in discarded region: offset to particular copy we want */
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#define per_cpu(var, cpu) (*({ \
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extern int simple_indentifier_##var(void); \
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RELOC_HIDE(&per_cpu__##var, __per_cpu_offset[cpu]); }))
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#define __raw_get_cpu_var(var) (*({ \
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extern int simple_indentifier_##var(void); \
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RELOC_HIDE(&per_cpu__##var, x86_read_percpu(this_cpu_off)); \
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}))
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#define __get_cpu_var(var) __raw_get_cpu_var(var)
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/* A macro to avoid #include hell... */
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#define percpu_modcopy(pcpudst, src, size) \
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do { \
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unsigned int __i; \
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for_each_possible_cpu(__i) \
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memcpy((pcpudst)+__per_cpu_offset[__i], \
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(src), (size)); \
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} while (0)
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#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
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#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
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/* fs segment starts at (positive) offset == __per_cpu_offset[cpu] */
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#define __percpu_seg "%%fs:"
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#else /* !SMP */
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#include <asm-generic/percpu.h>
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#define __percpu_seg ""
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#endif /* SMP */
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/* For arch-specific code, we can use direct single-insn ops (they
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* don't give an lvalue though). */
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extern void __bad_percpu_size(void);
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#define percpu_to_op(op,var,val) \
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do { \
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typedef typeof(var) T__; \
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if (0) { T__ tmp__; tmp__ = (val); } \
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switch (sizeof(var)) { \
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case 1: \
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asm(op "b %1,"__percpu_seg"%0" \
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: "+m" (var) \
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:"ri" ((T__)val)); \
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break; \
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case 2: \
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asm(op "w %1,"__percpu_seg"%0" \
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: "+m" (var) \
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:"ri" ((T__)val)); \
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break; \
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case 4: \
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asm(op "l %1,"__percpu_seg"%0" \
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: "+m" (var) \
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:"ri" ((T__)val)); \
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break; \
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default: __bad_percpu_size(); \
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} \
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} while (0)
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#define percpu_from_op(op,var) \
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({ \
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typeof(var) ret__; \
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switch (sizeof(var)) { \
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case 1: \
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asm(op "b "__percpu_seg"%1,%0" \
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: "=r" (ret__) \
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: "m" (var)); \
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break; \
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case 2: \
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asm(op "w "__percpu_seg"%1,%0" \
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: "=r" (ret__) \
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: "m" (var)); \
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break; \
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case 4: \
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asm(op "l "__percpu_seg"%1,%0" \
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: "=r" (ret__) \
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: "m" (var)); \
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break; \
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default: __bad_percpu_size(); \
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} \
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ret__; })
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#define x86_read_percpu(var) percpu_from_op("mov", per_cpu__##var)
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#define x86_write_percpu(var,val) percpu_to_op("mov", per_cpu__##var, val)
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#define x86_add_percpu(var,val) percpu_to_op("add", per_cpu__##var, val)
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#define x86_sub_percpu(var,val) percpu_to_op("sub", per_cpu__##var, val)
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#define x86_or_percpu(var,val) percpu_to_op("or", per_cpu__##var, val)
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#endif /* !__ASSEMBLY__ */
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#endif /* __ARCH_I386_PERCPU__ */
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