lib: Reduce timerwheel CPU consumption

The timerwheel is checked during IPC calls (fevent, flow_read),
causing huge load on CPU consumption in IPCPs, since they have a lot
of fevent() threads for QoS. The timerwheel will need further
optimization), but for now I reduced the default tick time to 5 ms and
added a boolean to check that the wheel is actually used.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

2 files changed, 10 insertions, 1 deletions

diff --git a/src/lib/CMakeLists.txt b/src/lib/CMakeLists.txt
index e6d175d3..76d0530d 100644
--- a/src/lib/CMakeLists.txt
+++ b/src/lib/CMakeLists.txt
@@ -200,7 +200,7 @@ set(FRCT_START_WINDOW 64 CACHE STRING
   "Start window, must be a power of 2")
 set(FRCT_RTO_MIN 250 CACHE STRING
   "Minimum Retransmission Timeout (RTO) for FRCT (us)")
-set(FRCT_TICK_TIME 500 CACHE STRING
+set(FRCT_TICK_TIME 5000 CACHE STRING
   "Tick time for FRCT activity (retransmission, acknowledgments) (us)")
 set(RXM_BUFFER_ON_HEAP FALSE CACHE BOOL
   "Store packets for retransmission on the heap instead of in packet buffer")
diff --git a/src/lib/timerwheel.c b/src/lib/timerwheel.c
index cd3074cb..a9f3c72a 100644
--- a/src/lib/timerwheel.c
+++ b/src/lib/timerwheel.c
@@ -65,6 +65,8 @@ struct {
         size_t           prv_rxm; /* Last processed rxm slot at lvl 0. */
         size_t           prv_ack; /* Last processed ack slot.          */
         pthread_mutex_t  lock;
+
+        bool             in_use;
 } rw;
 
 static void timerwheel_fini(void)
@@ -140,6 +142,9 @@ static void timerwheel_move(void)
         size_t             i;
         size_t             j;
 
+        if (!__sync_bool_compare_and_swap(&rw.in_use, true, true))
+                return;
+
         pthread_mutex_lock(&rw.lock);
 
         pthread_cleanup_push((void (*) (void *)) pthread_mutex_unlock,
@@ -373,6 +378,8 @@ static int timerwheel_rxm(struct frcti *       frcti,
 #endif
         pthread_mutex_unlock(&rw.lock);
 
+        __sync_bool_compare_and_swap(&rw.in_use, false, true);
+
         return 0;
 }
 
@@ -416,5 +423,7 @@ static int timerwheel_ack(int            fd,
 
         pthread_mutex_unlock(&rw.lock);
 
+        __sync_bool_compare_and_swap(&rw.in_use, false, true);
+
         return 0;
 }