Minimum GOMAXPROCS should be 1

internal/runtime/runtime.go

@@ -31,6 +31,3 @@ const (
 	// CPUQuotaMinUsed is return when CPU quota is larger than the min value
 	CPUQuotaMinUsed
 )
-
-// MinGOMAXPROCS defines the minimum value for GOMAXPROCS
-const MinGOMAXPROCS = 2

maxprocs/maxprocs.go

@@ -37,8 +37,9 @@ func currentMaxProcs() int {
 }
 
 type config struct {
-	printf func(string, ...interface{})
-	procs  func(int) (int, iruntime.CPUQuotaStatus, error)
+	printf        func(string, ...interface{})
+	procs         func(int) (int, iruntime.CPUQuotaStatus, error)
+	minGOMAXPROCS int
 }
 
 func (c *config) log(fmt string, args ...interface{}) {
@@ -60,6 +61,16 @@ func Logger(printf func(string, ...interface{})) Option {
 	})
 }
 
+// Min sets the minimum GOMAXPROCS value that will be used.
+// Any value below 1 is ignored.
+func Min(n int) Option {
+	return optionFunc(func(cfg *config) {
+		if n >= 1 {
+			cfg.minGOMAXPROCS = n
+		}
+	})
+}
+
 type optionFunc func(*config)
 
 func (of optionFunc) apply(cfg *config) { of(cfg) }
@@ -70,7 +81,10 @@ func (of optionFunc) apply(cfg *config) { of(cfg) }
 // Set is a no-op on non-Linux systems and in Linux environments without a
 // configured CPU quota.
 func Set(opts ...Option) (func(), error) {
-	cfg := &config{procs: iruntime.CPUQuotaToGOMAXPROCS}
+	cfg := &config{
+		procs:         iruntime.CPUQuotaToGOMAXPROCS,
+		minGOMAXPROCS: 1,
+	}
 	for _, o := range opts {
 		o.apply(cfg)
 	}
@@ -87,7 +101,7 @@ func Set(opts ...Option) (func(), error) {
 		return undoNoop, nil
 	}
 
-	maxProcs, status, err := cfg.procs(iruntime.MinGOMAXPROCS)
+	maxProcs, status, err := cfg.procs(cfg.minGOMAXPROCS)
 	if err != nil {
 		return undoNoop, err
 	}

maxprocs/maxprocs_test.go

@@ -138,15 +138,29 @@ func TestSet(t *testing.T) {
 		quotaOpt := stubProcs(func(min int) (int, iruntime.CPUQuotaStatus, error) {
 			return min, iruntime.CPUQuotaMinUsed, nil
 		})
-		undo, err := Set(logOpt, quotaOpt)
+		undo, err := Set(logOpt, quotaOpt, Min(5))
+		defer undo()
+		require.NoError(t, err, "Set failed")
+		assert.Equal(t, 5, currentMaxProcs(), "should use min allowed GOMAXPROCS")
+		assert.Contains(t, buf.String(), "using minimum allowed", "unexpected log output")
+	})
+
+	t.Run("Min unused", func(t *testing.T) {
+		buf, logOpt := testLogger()
+		quotaOpt := stubProcs(func(min int) (int, iruntime.CPUQuotaStatus, error) {
+			return min, iruntime.CPUQuotaMinUsed, nil
+		})
+		// Min(-1) should be ignored.
+		undo, err := Set(logOpt, quotaOpt, Min(5), Min(-1))
 		defer undo()
 		require.NoError(t, err, "Set failed")
-		assert.Equal(t, iruntime.MinGOMAXPROCS, currentMaxProcs(), "should use min allowed GOMAXPROCS")
+		assert.Equal(t, 5, currentMaxProcs(), "should use min allowed GOMAXPROCS")
 		assert.Contains(t, buf.String(), "using minimum allowed", "unexpected log output")
 	})
 
 	t.Run("QuotaUsed", func(t *testing.T) {
 		opt := stubProcs(func(min int) (int, iruntime.CPUQuotaStatus, error) {
+			assert.Equal(t, 1, min, "Default minimum value should be 1")
 			return 42, iruntime.CPUQuotaUsed, nil
 		})
 		undo, err := Set(opt)