[lkml]   [2011]   [Mar]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
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 <> 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.)


 \ /
  Last update: 2011-03-30 18:21    [W:0.108 / U:31.948 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site