Re: [Xen-devel] [PATCH 1/4] xen/p2m: Optimize the get_phys_to_machine function a bit.

[David Vrabel <david.vrabel@citrix.com>]

On 03/07/12 16:40, Konrad Rzeszutek Wilk wrote:
> Running perf tells me that the check for p2m_identity
> is done a lot - more than it should.

This patch doesn't change the how often the check is done.  Is this just
bad wording of the description?
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  arch/x86/xen/p2m.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> index 64effdc..161bcdc 100644
> --- a/arch/x86/xen/p2m.c
> +++ b/arch/x86/xen/p2m.c
> @@ -406,7 +406,7 @@ unsigned long get_phys_to_machine(unsigned long pfn)
>  	 * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
>  	 * would be wrong.
>  	 */
> -	if (p2m_top[topidx][mididx] == p2m_identity)
> +	if (unlikely(p2m_top[topidx][mididx] == p2m_identity))
>  		return IDENTITY_FRAME(pfn);
>  
>  	return p2m_top[topidx][mididx][idx];