Timer wheel divided into a "soon wheel" and a "later wheel"

The old single wheel implementation handled about 65 seconds. The
new dual wheel implementation handles more than 37 hours. The dual
wheels have also been shrunk compared to the single wheel, so the
total memory consumption for timer wheels have been cut in half.

1 files changed, 43 insertions, 7 deletions

diff --git a/erts/emulator/beam/erl_time.h b/erts/emulator/beam/erl_time.h
index 00b4a84b4a..699e69e991 100644
--- a/erts/emulator/beam/erl_time.h
+++ b/erts/emulator/beam/erl_time.h
@@ -21,19 +21,52 @@
 #ifndef ERL_TIME_H__
 #define ERL_TIME_H__
 
-/* timer wheel size NEED to be a power of 2 */
-#ifdef SMALL_MEMORY
-#define ERTS_TIW_SIZE (1 << 13)
-#else
-#define ERTS_TIW_SIZE (1 << 16)
+#if 0
+#  define ERTS_TW_DEBUG
+#endif
+#if defined(DEBUG) && !defined(ERTS_TW_DEBUG)
+#  define ERTS_TW_DEBUG
 #endif
 
-#if defined(DEBUG) || 0
+#if defined(ERTS_TW_DEBUG)
 #define ERTS_TIME_ASSERT(B) ERTS_ASSERT(B)
 #else
 #define ERTS_TIME_ASSERT(B) ((void) 1)
 #endif
 
+#ifdef ERTS_TW_DEBUG
+/*
+ * Soon wheel will handle about 1 seconds
+ * Later wheel will handle about 8 minutes
+ */
+#  define ERTS_TW_SOON_WHEEL_BITS 10
+#  define ERTS_TW_LATER_WHEEL_BITS 10
+#else
+#  ifdef SMALL_MEMORY
+/*
+ * Soon wheel will handle about 4 seconds
+ * Later wheel will handle about 2 hours and 19 minutes
+ */
+#    define ERTS_TW_SOON_WHEEL_BITS 12
+#    define ERTS_TW_LATER_WHEEL_BITS 12
+#  else
+/*
+ * Soon wheel will handle about 16 seconds
+ * Later wheel will handle about 37 hours and 16 minutes
+ */
+#    define ERTS_TW_SOON_WHEEL_BITS 14
+#    define ERTS_TW_LATER_WHEEL_BITS 14
+#  endif
+#endif
+
+/*
+ * Number of slots in each timer wheel...
+ *
+ * These *need* to be a power of 2
+ */
+#define ERTS_TW_SOON_WHEEL_SIZE (1 << ERTS_TW_SOON_WHEEL_BITS)
+#define ERTS_TW_LATER_WHEEL_SIZE (1 << ERTS_TW_LATER_WHEEL_BITS)
+
 typedef enum {
     ERTS_NO_TIME_WARP_MODE,
     ERTS_SINGLE_TIME_WARP_MODE,
@@ -103,7 +136,10 @@ Eterm erts_system_time_source(struct process*c_p);
 #define ERTS_CLKTCK_RESOLUTION (erts_time_sup__.r.o.clktck_resolution)
 #endif
 
-#define ERTS_TIMER_WHEEL_MSEC (ERTS_TIW_SIZE/(ERTS_CLKTCK_RESOLUTION/1000))
+#define ERTS_TW_SOON_WHEEL_MSEC (ERTS_TW_SOON_WHEEL_SIZE/(ERTS_CLKTCK_RESOLUTION/1000))
+#define ERTS_TW_LATER_WHEEL_MSEC (ERTS_TW_LATER_WHEEL_SIZE*ERTS_TW_SOON_WHEEL_MSEC/2)
+
+#define ERTS_TIMER_WHEEL_MSEC ERTS_TW_LATER_WHEEL_MSEC
 
 struct erts_time_sup_read_only__ {
     ErtsMonotonicTime monotonic_time_unit;