perf/x86/intel: Optimize intel_get_excl_constraints()

Avoid the POPCNT  by noting we can decrement the weight for each
cleared bit.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Stephane Eranian <eranian@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 879ab540fd05781a432cfbc73a22a0b74e472b92..a80015fa8aeda654cfe5af768fcedd5c52980ee3 100644 (file)
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2838,7 +2838,7 @@ intel_get_excl_constraints(struct cpu_hw_events *cpuc, struct perf_event *event,
        struct intel_excl_cntrs *excl_cntrs = cpuc->excl_cntrs;
        struct intel_excl_states *xlo;
        int tid = cpuc->excl_thread_id;
-       int is_excl, i;
+       int is_excl, i, w;
 
        /*
         * validating a group does not require
@@ -2894,36 +2894,40 @@ intel_get_excl_constraints(struct cpu_hw_events *cpuc, struct perf_event *event,
         * SHARED   : sibling counter measuring non-exclusive event
         * UNUSED   : sibling counter unused
         */
+       w = c->weight;
        for_each_set_bit(i, c->idxmsk, X86_PMC_IDX_MAX) {
                /*
                 * exclusive event in sibling counter
                 * our corresponding counter cannot be used
                 * regardless of our event
                 */
-               if (xlo->state[i] == INTEL_EXCL_EXCLUSIVE)
+               if (xlo->state[i] == INTEL_EXCL_EXCLUSIVE) {
                        __clear_bit(i, c->idxmsk);
+                       w--;
+                       continue;
+               }
                /*
                 * if measuring an exclusive event, sibling
                 * measuring non-exclusive, then counter cannot
                 * be used
                 */
-               if (is_excl && xlo->state[i] == INTEL_EXCL_SHARED)
+               if (is_excl && xlo->state[i] == INTEL_EXCL_SHARED) {
                        __clear_bit(i, c->idxmsk);
+                       w--;
+                       continue;
+               }
        }
 
-       /*
-        * recompute actual bit weight for scheduling algorithm
-        */
-       c->weight = hweight64(c->idxmsk64);
-
        /*
         * if we return an empty mask, then switch
         * back to static empty constraint to avoid
         * the cost of freeing later on
         */
-       if (c->weight == 0)
+       if (!w)
                c = &emptyconstraint;
 
+       c->weight = w;
+
        return c;
 }