Messages in this thread | | | Date | Wed, 6 Jun 2012 07:16:44 -0700 | From | Andi Kleen <> | Subject | Re: [PATCH 5/5] perf, x86: Prefer RDPMC over RDMSR for reading counters |
| |
On Wed, Jun 06, 2012 at 12:46:19PM +0200, Peter Zijlstra wrote: > On Tue, 2012-06-05 at 17:56 -0700, Andi Kleen wrote: > > From: Andi Kleen <ak@linux.intel.com> > > > > RDPMC is much faster than RDMSR for reading performance counters, > > since it's not serializing. Use it if possible in the perf handler. > > > > Only tested on Sandy Bridge, so I only enabled it there so far. > > That's just stupid.. I took Vince's patch from a while back.
What do you mean? It's significantly faster to read the counters this way, because it avoids serialization and other overhead.
Vince's patch only enabled it for user space I believe, This is for lowering the kernel PMI handler overhead.
-Andi
-- ak@linux.intel.com -- Speaking for myself only
| |