From d263e855977d49719ceea4da3b843bab5951dffb Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Mon, 5 Jun 2017 10:59:57 -0400 Subject: [PATCH] runtime: expand acceptable PingPongHog factor from 2 to 5 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Since TestPingPongHog tests the scheduler, it's ultimately probabilistic. Currently, it requires the result be at most of factor of 2 off of the ideal. It turns out this isn't quite enough in practice, with factors on 1000 iterations on linux/amd64 ranging from 0.48 to 2.5. If the test were failing, we would expect a factor closer to 1000X, so it's pretty safe to expand the accepted factor from 2 to 5. Fixes #20494. Change-Id: If8f2e96194fe66f1fb981a965d1167fe74ff38d7 Reviewed-on: https://go-review.googlesource.com/44859 Run-TryBot: Austin Clements Reviewed-by: Daniel Martí Reviewed-by: Brad Fitzpatrick TryBot-Result: Gobot Gobot --- src/runtime/proc_test.go | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/src/runtime/proc_test.go b/src/runtime/proc_test.go index e7c0f3333e..90a6cab874 100644 --- a/src/runtime/proc_test.go +++ b/src/runtime/proc_test.go @@ -428,10 +428,13 @@ func TestPingPongHog(t *testing.T) { <-lightChan // Check that hogCount and lightCount are within a factor of - // 2, which indicates that both pairs of goroutines handed off - // the P within a time-slice to their buddy. - if hogCount > lightCount*2 || lightCount > hogCount*2 { - t.Fatalf("want hogCount/lightCount in [0.5, 2]; got %d/%d = %g", hogCount, lightCount, float64(hogCount)/float64(lightCount)) + // 5, which indicates that both pairs of goroutines handed off + // the P within a time-slice to their buddy. We can use a + // fairly large factor here to make this robust: if the + // scheduler isn't working right, the gap should be ~1000X. + const factor = 5 + if hogCount > lightCount*factor || lightCount > hogCount*factor { + t.Fatalf("want hogCount/lightCount in [%v, %v]; got %d/%d = %g", 1.0/factor, factor, hogCount, lightCount, float64(hogCount)/float64(lightCount)) } }