• Alexander Duyck's avatar
    x86: Improve __phys_addr performance by making use of carry flags and inlining · 0bdf525f
    Alexander Duyck authored
    This patch is meant to improve overall system performance when making use of
    the __phys_addr call.  To do this I have implemented several changes.
    
    First if CONFIG_DEBUG_VIRTUAL is not defined __phys_addr is made an inline,
    similar to how this is currently handled in 32 bit.  However in order to do
    this it is required to export phys_base so that it is available if __phys_addr
    is used in kernel modules.
    
    The second change was to streamline the code by making use of the carry flag
    on an add operation instead of performing a compare on a 64 bit value.  The
    advantage to this is that it allows us to significantly reduce the overall
    size of the call.  On my Xeon E5 system the entire __phys_addr inline call
    consumes a little less than 32 bytes and 5 instructions.  I also applied
    similar logic to the debug version of the function.  My testing shows that the
    debug version of the function with this patch applied is slightly faster than
    the non-debug version without the patch.
    
    Finally I also applied the same logic changes to __virt_addr_valid since it
    used the same general code flow as __phys_addr and could achieve similar gains
    though these changes.
    Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@intel.com>
    Link: http://lkml.kernel.org/r/20121116215315.8521.46270.stgit@ahduyck-cp1.jf.intel.comSigned-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
    0bdf525f
physaddr.c 1.69 KB