linux-kernel - Re: [patch 3/3]use new macros for x86 percpu readmostly section

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Date:	Fri, 10 Dec 2010 08:21:52 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"sam@...nborg.org" <sam@...nborg.org>,
	"eric.dumazet@...il.com" <eric.dumazet@...il.com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [patch 3/3]use new macros for x86 percpu readmostly section

On Fri, 2010-12-10 at 06:32 +0800, Andrew Morton wrote:
> On Thu, 02 Dec 2010 10:02:30 +0800
> Shaohua Li <shaohua.li@...el.com> wrote:
> 
> > Use the new macros to correctly align percpu readmostly data.
> > 
> > Signed-off-by: Shaohua Li <shaohua.li@...el.com>
> > ---
> >  arch/x86/kernel/vmlinux.lds.S |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > Index: linux/arch/x86/kernel/vmlinux.lds.S
> > ===================================================================
> > --- linux.orig/arch/x86/kernel/vmlinux.lds.S	2010-12-02 09:48:44.000000000 +0800
> > +++ linux/arch/x86/kernel/vmlinux.lds.S	2010-12-02 09:54:24.000000000 +0800
> > @@ -226,7 +226,7 @@ SECTIONS
> >  	 * output PHDR, so the next output section - .init.text - should
> >  	 * start another segment - init.
> >  	 */
> > -	PERCPU_VADDR(0, :percpu)
> > +	PERCPU_VADDR_CACHEALIGNED(0, :percpu, INTERNODE_CACHE_BYTES)
> >  #endif
> >  
> >  	INIT_TEXT_SECTION(PAGE_SIZE)
> > @@ -301,7 +301,7 @@ SECTIONS
> >  	}
> >  
> >  #if !defined(CONFIG_X86_64) || !defined(CONFIG_SMP)
> > -	PERCPU(THREAD_SIZE)
> > +	PERCPU_CACHEALIGNED(THREAD_SIZE, INTERNODE_CACHE_BYTES)
> >  #endif
> >  
> >  	. = ALIGN(PAGE_SIZE);
> > 
> 
> So what is the situation now with all other architectures?  Should they
> be changed to correctly align their read-mostly percpu areas?
> 
> If so, what should the arch maintainers do to achieve this?
Yes, other arch should use new macro too with correct cache alignment
(similar like the alignment for read-mostly section). But currently only
x86 has read-mostly percpu data.

Thanks,
Shaohua


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