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[PATCH 1/3] percpu: Add alloc_percpu_aligned()

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  [PATCH 1/3] percpu: Add alloc_percpu_aligned() "Huang, Ying" <ying.huang@intel.com> - 2017-08-02 11:00 +0200
    Re: [PATCH 1/3] percpu: Add alloc_percpu_aligned() Christopher Lameter <cl@linux.com> - 2017-08-02 16:00 +0200
      Re: [PATCH 1/3] percpu: Add alloc_percpu_aligned() "Huang\, Ying" <ying.huang@intel.com> - 2017-08-03 02:40 +0200

#1701926 — [PATCH 1/3] percpu: Add alloc_percpu_aligned()

From: Huang Ying <ying.huang@intel.com>

To allocate percpu memory that is aligned with cache line size
dynamically.  We can statically allocate percpu memory that is aligned
with cache line size with DEFINE_PER_CPU_ALIGNED(), but we have no
correspondent API for dynamic allocation.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
---
 include/linux/percpu.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 491b3f5a5f8a..8b80a965d64a 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -129,5 +129,8 @@ extern phys_addr_t per_cpu_ptr_to_phys(void *addr);
 #define alloc_percpu(type)						\
 	(typeof(type) __percpu *)__alloc_percpu(sizeof(type),		\
 						__alignof__(type))
+#define alloc_percpu_aligned(type)					\
+	((typeof(type) __percpu *)__alloc_percpu(sizeof(type),		\
+		max_t(unsigned int, cache_line_size(), __alignof__(type))))
 
 #endif /* __LINUX_PERCPU_H */
-- 
2.13.2

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#1702126

On Wed, 2 Aug 2017, Huang, Ying wrote:

> --- a/include/linux/percpu.h
> +++ b/include/linux/percpu.h
> @@ -129,5 +129,8 @@ extern phys_addr_t per_cpu_ptr_to_phys(void *addr);
>  #define alloc_percpu(type)						\
>  	(typeof(type) __percpu *)__alloc_percpu(sizeof(type),		\
>  						__alignof__(type))
> +#define alloc_percpu_aligned(type)					\
> +	((typeof(type) __percpu *)__alloc_percpu(sizeof(type),		\
> +		max_t(unsigned int, cache_line_size(), __alignof__(type))))
>
>  #endif /* __LINUX_PERCPU_H */

This is not needeed since alloc_percpu() already uses __alignof__(type).

If you add an attribute to the definition of "type" that requires
cacheline alignmet (f.e. __cacheline_aligned) then alloc_percpu() will
align the allocation as you desire.

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#1702589

Christopher Lameter <cl@linux.com> writes:

> On Wed, 2 Aug 2017, Huang, Ying wrote:
>
>> --- a/include/linux/percpu.h
>> +++ b/include/linux/percpu.h
>> @@ -129,5 +129,8 @@ extern phys_addr_t per_cpu_ptr_to_phys(void *addr);
>>  #define alloc_percpu(type)						\
>>  	(typeof(type) __percpu *)__alloc_percpu(sizeof(type),		\
>>  						__alignof__(type))
>> +#define alloc_percpu_aligned(type)					\
>> +	((typeof(type) __percpu *)__alloc_percpu(sizeof(type),		\
>> +		max_t(unsigned int, cache_line_size(), __alignof__(type))))
>>
>>  #endif /* __LINUX_PERCPU_H */
>
> This is not needeed since alloc_percpu() already uses __alignof__(type).
>
> If you add an attribute to the definition of "type" that requires
> cacheline alignmet (f.e. __cacheline_aligned) then alloc_percpu() will
> align the allocation as you desire.

OK.

Best Regards,
Huang, Ying

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