perf/x86/intel/lbr: Optimize v4 LBR unfreezing
authorAndi Kleen <ak@linux.intel.com>
Sun, 10 May 2015 19:22:46 +0000 (12:22 -0700)
committerIngo Molnar <mingo@kernel.org>
Tue, 4 Aug 2015 08:16:58 +0000 (10:16 +0200)
In Arch perfmon v4 the GLOBAL_STATUS reset automatically unfreezes
LBRs. So no need to do it manually in the LBR code. Add a check
to skip it.

v2: Move test up to beginning of function.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1431285767-27027-9-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/kernel/cpu/perf_event_intel_lbr.c

index 2fb5737..769a42f 100644 (file)
@@ -141,6 +141,13 @@ static void __intel_pmu_lbr_enable(bool pmi)
        u64 debugctl, lbr_select = 0, orig_debugctl;
 
        /*
+        * No need to unfreeze manually, as v4 can do that as part
+        * of the GLOBAL_STATUS ack.
+        */
+       if (pmi && x86_pmu.version >= 4)
+               return;
+
+       /*
         * No need to reprogram LBR_SELECT in a PMI, as it
         * did not change.
         */