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Subject: Re: [tip:x86/mm] percpu: Introduce a read-mostly percpu API
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Shaohua Li <shaohua.li@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
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Date: Thu, 21 Oct 2010 08:48:05 +0200
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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...