linux-kernel - Re: [PATCH] spufs: always map local store non-guarded

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Message-Id: <1162513734.8999.11.camel@localhost.localdomain>
Date:	Fri, 03 Nov 2006 11:28:54 +1100
From:	Michael Ellerman <michael@...erman.id.au>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Paul Mackerras <paulus@...ba.org>, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org, cbe-oss-dev <cbe-oss-dev@...abs.org>
Subject: Re: [PATCH] spufs: always map local store non-guarded

On Thu, 2006-11-02 at 13:46 +0100, Arnd Bergmann wrote:
> When fixing spufs to map the 'mem' file backing store cacheable,
> I incorrectly set the physical mapping to use both cache-inhibited
> and guarded mapping, which resulted in a serious performance
> degradation.
> 
> Accessing the real local store memory needs to be cache-inhibited,
> in order to maintain data consistency, but since it is actual
> RAM, there is no point in a guarded mapping.
> 
> Debugged-by: Michael Ellerman <michael@...erman.id.au>
> Signed-off-by: Arnd Bergmann <arnd.bergmann@...ibm.com>
> ---

Looks good, cheers

Acked-by: Michael Ellerman <michael@...erman.id.au>

> 
> This fixes a regression in 2.6.19, please merge.
> 
> Index: linux-2.6/arch/powerpc/platforms/cell/spufs/file.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/file.c
> +++ linux-2.6/arch/powerpc/platforms/cell/spufs/file.c
> @@ -104,11 +104,11 @@ spufs_mem_mmap_nopage(struct vm_area_str
>  
>  	if (ctx->state == SPU_STATE_SAVED) {
>  		vma->vm_page_prot = __pgprot(pgprot_val(vma->vm_page_prot)
> -					& ~(_PAGE_NO_CACHE | _PAGE_GUARDED));
> +							& ~_PAGE_NO_CACHE);
>  		page = vmalloc_to_page(ctx->csa.lscsa->ls + offset);
>  	} else {
>  		vma->vm_page_prot = __pgprot(pgprot_val(vma->vm_page_prot)
> -					| _PAGE_NO_CACHE | _PAGE_GUARDED);
> +							| _PAGE_NO_CACHE);
>  		page = pfn_to_page((ctx->spu->local_store_phys + offset)
>  				   >> PAGE_SHIFT);
>  	}
-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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