Re: [PATCH v6 3/6] perf: Use min_heap in visit_groups_merge

[Peter Zijlstra]

On Thu, Feb 13, 2020 at 11:51:30PM -0800, Ian Rogers wrote:
>  
> -		*evt = perf_event_groups_next(*evt);
> +		next = perf_event_groups_next(itrs[0]);
> +		if (next) {
> +			min_heap_pop_push(&event_heap, &next,
> +					&perf_min_heap);
> +		} else
> +			min_heap_pop(&event_heap, &perf_min_heap);
>  	}

Like this:

@@ -3585,9 +3581,9 @@ static noinline int visit_groups_merge(s
 		if (ret)
 			return ret;
 
-		next = perf_event_groups_next(*evt);
-		if (next)
-			min_heap_pop_push(&event_heap, &next, &perf_min_heap);
+		*evt = perf_event_groups_next(*evt);
+		if (*evt)
+			min_heapify(&event_heap, 0, &perf_min_heap);
 		else
 			min_heap_pop(&event_heap, &perf_min_heap);
 	}

That's an 'obvious' replace and resort and obviates the need for that
weird pop that doesn't return nothing operation.