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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>
This commit is contained in:
Peter Zijlstra 2019-03-14 13:01:14 +01:00 committed by Ingo Molnar
parent 1f6a1e2d7d
commit c090cb70c6
1 changed files with 13 additions and 9 deletions
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22
arch/x86/events/intel/core.c
View File

@ -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;
}