Benchmarks for searchv2 (#60730)

* bench-test

* cleanup

* more simplification

* fix tests

* correct wrong argument ordering & use constant

* fix issues with tests setup

* add benchmark results

* reuse Gabriel's concurrent setup code

* correct error logs for ac benchmarks

pkg/services/accesscontrol/actest/common.go

@@ -0,0 +1,61 @@
+package actest
+
+import "sync"
+
+const Concurrency = 10
+const BatchSize = 1000
+
+type bounds struct {
+	start, end int
+}
+
+// ConcurrentBatch spawns the requested amount of workers then ask them to run eachFn on chunks of the requested size
+func ConcurrentBatch(workers, count, size int, eachFn func(start, end int) error) error {
+	var wg sync.WaitGroup
+	alldone := make(chan bool) // Indicates that all workers have finished working
+	chunk := make(chan bounds) // Gives the workers the bounds they should work with
+	ret := make(chan error)    // Allow workers to notify in case of errors
+	defer close(ret)
+
+	// Launch all workers
+	for x := 0; x < workers; x++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for ck := range chunk {
+				if err := eachFn(ck.start, ck.end); err != nil {
+					ret <- err
+					return
+				}
+			}
+		}()
+	}
+
+	go func() {
+		// Tell the workers the chunks they have to work on
+		for i := 0; i < count; {
+			end := i + size
+			if end > count {
+				end = count
+			}
+
+			chunk <- bounds{start: i, end: end}
+
+			i = end
+		}
+		close(chunk)
+
+		// Wait for the workers
+		wg.Wait()
+		close(alldone)
+	}()
+
+	// wait for an error or for all workers to be done
+	select {
+	case err := <-ret:
+		return err
+	case <-alldone:
+		break
+	}
+	return nil
+}