Add a simple adjustTimeoutByDetectedHz to compute a suitable timeout/naptime based on base VESPA_TIMER_HZ to use for random waiting

when doing a poll based appraoch.

3 files changed, 27 insertions, 0 deletions

diff --git a/vespalib/src/tests/time/time_test.cpp b/vespalib/src/tests/time/time_test.cpp
index c2858308006..0ca583c8326 100644
--- a/vespalib/src/tests/time/time_test.cpp
+++ b/vespalib/src/tests/time/time_test.cpp
@@ -68,4 +68,19 @@ TEST(TimeTest, default_timer_frequency_is_1000_hz) {
     EXPECT_EQ(1000u, getVespaTimerHz());
 }
 
+TEST(TimeTest, timeout_is_relative_to_frequency) {
+    EXPECT_EQ(1000u, getVespaTimerHz());
+
+    EXPECT_EQ(1ms, adjustTimeoutByDetectedHz(1ms));
+    EXPECT_EQ(20ms, adjustTimeoutByDetectedHz(20ms));
+
+    EXPECT_EQ(1ms, adjustTimeoutByHz(1ms, 1000));
+    EXPECT_EQ(10ms, adjustTimeoutByHz(1ms, 100));
+    EXPECT_EQ(100ms, adjustTimeoutByHz(1ms, 10));
+
+    EXPECT_EQ(20ms, adjustTimeoutByHz(20ms, 1000));
+    EXPECT_EQ(200ms, adjustTimeoutByHz(20ms, 100));
+    EXPECT_EQ(2000ms, adjustTimeoutByHz(20ms, 10));
+}
+
 GTEST_MAIN_RUN_ALL_TESTS()
diff --git a/vespalib/src/vespa/vespalib/util/time.cpp b/vespalib/src/vespa/vespalib/util/time.cpp
index bcc289489ea..3737a25f268 100644
--- a/vespalib/src/vespa/vespalib/util/time.cpp
+++ b/vespalib/src/vespa/vespalib/util/time.cpp
@@ -30,6 +30,16 @@ getVespaTimerHz() {
     return 1000u;
 }
 
+duration
+adjustTimeoutByHz(duration timeout, long hz) {
+    return  (timeout * 1000) / hz;
+}
+
+duration
+adjustTimeoutByDetectedHz(duration timeout) {
+    return  adjustTimeoutByHz(timeout, getVespaTimerHz());
+}
+
 namespace {
 
 string
diff --git a/vespalib/src/vespa/vespalib/util/time.h b/vespalib/src/vespa/vespalib/util/time.h
index dbbae862a8d..783831b5171 100644
--- a/vespalib/src/vespa/vespalib/util/time.h
+++ b/vespalib/src/vespa/vespalib/util/time.h
@@ -92,5 +92,7 @@ public:
  * The default frequency (1000hz) for vespa timer, with environment override VESPA_TIMER_HZ capped to [1..1000]
  */
 uint32_t getVespaTimerHz();
+duration adjustTimeoutByDetectedHz(duration timeout);
+duration adjustTimeoutByHz(duration timeout, long hz);
 
 }