doc/go1.17: mention block profile bias fix

Change-Id: I76fd872b2d74704396f0683ffa9cec40b7027247
Reviewed-on: https://go-review.googlesource.com/c/go/+/324471
Reviewed-by: Heschi Kreinick <heschi@google.com>
Trust: Dmitri Shuralyov <dmitshur@golang.org>

doc/go1.17.html

@@ -725,6 +725,16 @@ Do not send CLs removing the interior tags from such phrases.
   </dd>
 </dl><!-- runtime/metrics -->
 
+
+<dl id="runtime/pprof"><dt><a href="/pkg/runtime/pprof">runtime/pprof</a></dt>
+  <dd>
+    <p><!-- CL 299991 -->
+      Block profiles are no longer biased to favor infrequent long events over
+      frequent short events.
+    </p>
+  </dd>
+</dl><!-- runtime/pprof -->
+
 <dl id="strconv"><dt><a href="/pkg/strconv/">strconv</a></dt>
   <dd>
     <p><!-- CL 170079 -->

src/runtime/pprof/pprof_test.go

@@ -106,6 +106,28 @@ func TestCPUProfileMultithreaded(t *testing.T) {
 	})
 }
 
+func TestCPUProfileThreadBias(t *testing.T) {
+	cpuHogA := func(dur time.Duration) {
+		cpuHogger(cpuHog1, &salt2, dur)
+	}
+
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
+	prof := testCPUProfile(t, stackContains, []string{"runtime/pprof.cpuHog1", "runtime/pprof.cpuHog2"}, avoidFunctions(), func(dur time.Duration) {
+		//c := make(chan int)
+		//go func() {
+		//cpuHogger(cpuHog1, &salt1, dur)
+		//c <- 1
+		//}()
+		cpuHogA(dur)
+		//<-c
+	})
+	fmt.Printf("%#v\n", prof)
+}
+
+func cpuHogA(dur time.Duration) {
+	cpuHogger(cpuHog1, &salt2, dur)
+}
+
 // containsInlinedCall reports whether the function body for the function f is
 // known to contain an inlined function call within the first maxBytes bytes.
 func containsInlinedCall(f interface{}, maxBytes int) bool {