On Mon, Jul 09, 2012 at 04:41:24PM +0100, David Vrabel wrote: > 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?
Its bad wording plus it really does not change the assmebler code - I thought it did but since there is only one "if" case it does not matter how much I put unlikely in front of it - it is the only branch condition. Perhaps if I make the code be put in a variable (register) that would optimize this a bit more... > > > > Signed-off-by: Konrad Rzeszutek Wilk <[email protected]> > > --- > > 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]; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
