linux-kernel - Re: [patch 2/3] add new macros to make percpu readmostly section correctly align

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Date:	Tue, 28 Dec 2010 08:26:57 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Tejun Heo <htejun@...il.com>
Cc:	Sam Ravnborg <sam@...nborg.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"eric.dumazet@...il.com" <eric.dumazet@...il.com>
Subject: Re: [patch 2/3] add new macros to make percpu readmostly section
 correctly align

On Mon, 2010-12-27 at 20:14 +0800, Tejun Heo wrote:
> On Thu, Dec 23, 2010 at 10:38:34AM +0800, Shaohua Li wrote:
> > The first patch in the series isn't related to this issue, please
> > consider merge it.
> 
> Can you please re-post it?  Thanks.
here it is.

Subject: make readmostly section correctly align

readmostly section should end at cache line aligned address, otherwise the last
several data might share cachline with other data and make the readmostly data
still have cache bounce.
For example, in ia64, secpath_cachep is the last readmostly data, and it shares
cacheline with init_uts_ns.
a000000100e80480 d secpath_cachep
a000000100e80488 D init_uts_ns

Signed-off-by: Shaohua Li <shaohua.li@...el.com>

---
 include/asm-generic/vmlinux.lds.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux.orig/include/asm-generic/vmlinux.lds.h	2010-12-01 16:49:48.000000000 +0800
+++ linux/include/asm-generic/vmlinux.lds.h	2010-12-02 09:22:32.000000000 +0800
@@ -192,7 +192,8 @@
 
 #define READ_MOSTLY_DATA(align)						\
 	. = ALIGN(align);						\
-	*(.data..read_mostly)
+	*(.data..read_mostly)						\
+	. = ALIGN(align);
 
 #define CACHELINE_ALIGNED_DATA(align)					\
 	. = ALIGN(align);						\


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