lkml.org 
[lkml]   [2011]   [Mar]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH tip:x86/mm 1/3] x86: A fast way to check capabilities of the current cpu
    On 03/30/2011 08:58 AM, H. Peter Anvin wrote:
    > On 03/14/2011 12:49 PM, Andi Kleen wrote:
    >> Tejun Heo <tj@kernel.org> writes:
    >>
    >>> Add this_cpu_has() which determines if the current cpu has a certain
    >>> ability using a segment prefix and a bit test operation.
    >>
    >>
    >> Hmm: if the CPU capability is really tested in a performance critical
    >> path, wouldn't it even be better to just use static_branch() now?
    >>
    >
    > We have static_cpu_has() for this specific purpose (it actually predates
    > static_branch()).
    >

    Note that static_cpu_has() has two caveats:

    1. Before alternatives patching, it will always be false.
    2. It is the equivalent of boot_cpu_has(), i.e. the intersection of all
    the CPU feature sets (available at boot time, obviously.)

    -hpa


    \
     
     \ /
      Last update: 2011-03-30 18:21    [W:0.042 / U:1.456 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site