test: deflake locklinear again

Fixes #19276.

Change-Id: I64f8f80331d09956b6698c0b004ed7f7d70857fc
Reviewed-on: https://go-review.googlesource.com/39591
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

diff --git a/test/locklinear.go b/test/locklinear.go
index f1e912a2a3e381baec8099012f86b4038423611a..161912b65e84bc28b74494344f5a72111acb86a8 100644 (file)
--- a/test/locklinear.go
+++ b/test/locklinear.go
@@ -38,17 +38,25 @@ func checkLinear(typ string, tries int, f func(n int)) {
        n := tries
        fails := 0
        var buf bytes.Buffer
+       inversions := 0
        for {
                t1 := timeF(n)
                t2 := timeF(2 * n)
                if debug {
                        println(n, t1.String(), 2*n, t2.String())
                }
-               fmt.Fprintf(&buf, "%d %v %d %v\n", n, t1, 2*n, t2)
-               // should be 2x (linear); allow up to 2.5x
-               if t1*3/2 < t2 && t2 < t1*5/2 {
+               fmt.Fprintf(&buf, "%d %v %d %v (%.1fX)\n", n, t1, 2*n, t2, float64(t2)/float64(t1))
+               // should be 2x (linear); allow up to 3x
+               if t1*3/2 < t2 && t2 < t1*3 {
                        return
                }
+               if t2 < t1 {
+                       if inversions++; inversions >= 5 {
+                               // The system must be overloaded (some builders). Give up.
+                               return
+                       }
+                       continue // try again; don't increment fails
+               }
                // Once the test runs long enough for n ops,
                // try to get the right ratio at least once.
                // If many in a row all fail, give up.