Re: [RFC} memory unplug patchset prep [2/16] gathering alloc_zeroed_user_highpage()

[David Rientjes <rientjes@google.com>]

On Tue, 6 Mar 2007, KAMEZAWA Hiroyuki wrote:

> Definitions of alloc_zeroed_user_highpage() is scattered.
> This patch gathers them to linux/highmem.h
> 
> To do so, added CONFIG_ARCH_HAS_PREZERO_USERPAGE and
> CONFIG_ARCH_HAS_FLUSH_USERNEWZEROPAGE.
> 

Previous to this patch, __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE was never 
configurable by the user and was totally dependant on the architecture, 
which seems appropriate.  Are there cases when a user would actually 
prefer to disable the new CONFIG_ARCH_HAS_PREZERO_USERPAGE to avoid 
__GFP_ZERO allocations?

> Index: devel-tree-2.6.20-mm2/include/linux/highmem.h
> ===================================================================
> --- devel-tree-2.6.20-mm2.orig/include/linux/highmem.h
> +++ devel-tree-2.6.20-mm2/include/linux/highmem.h
> @@ -60,8 +60,22 @@ static inline void clear_user_highpage(s
>  	/* Make sure this page is cleared on other CPU's too before using it */
>  	smp_wmb();
>  }
> +#ifndef CONFIG_ARCH_HAS_FLUSH_USER_NEWZEROPAGE
> +#define flush_user_newzeroapge(page)	do{}while(0);
> +#endif
>  

Well, I guess this supports my point.  It doesn't appear as it was ever 
tested in disabling __GFP_ZERO allocations because 
flush_user_newzeropage() is misspelled above so it wouldn't even compile.

		David

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