Re: [tip:x86/mm] percpu: Introduce a read-mostly percpu API

H. Peter Anvin
2010-10-21T06:54:58Z

On 10/20/2010 11:48 PM, Eric Dumazet wrote:
> Le jeudi 21 octobre 2010 à 14:17 +0800, Shaohua Li a écrit :
>> This isn't a previous bug. see
>> #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
>> DECLARE_PER_CPU_SECTION(type, name, "..page_aligned") \
>> __aligned(PAGE_SIZE)
>> the ..page_aligned is already page aligned. I add it is because it can make
>> the .readmostly section guarantee to have no cache false sharing, because
>> I add the . = ALIGN(PAGE_SIZE); before .readmostly section, and .page_aligned
>> follows, but for sure this wates some memory.
>
> A small note:
>
> The __aligned(XXX) makes sure object _starts_ at XXX boundary, not that
> following one will also use same alignment. Of course, we can argue that
> we dont try to put in PAGE_ALIGNED section small objects, but still...
>
> Explicit .ALIGN() uses in .lds are more readable IMHO...
>

There is. However, see again my previous note about SORT_BY_ALIGNMENT.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.