tw_timer_expire_timers() - add a maximum to the number of expiration per call

The idea is to prevent a huge processing burst if, say, the network goes
down 10' for some reason, and so that we don't need to expire 1M timer
sessions on the first call.

The maximum is not an exact value, but a value after which the
expiration process is postponed until the next call.
That way, we don't have to process the same tick twice, nor to unlink
timers once at a time when processing a tick.
The fact that a timer slot could contain many entries should be dealt
with by changing the number of ticks per second.

Change-Id: I892d07f965094102a3d53e7dbf4e6f5ad22d4967
Signed-off-by: Gabriel Ganne <gabriel.ganne@enea.com>

diff --git a/src/vppinfra/tw_timer_template.c b/src/vppinfra/tw_timer_template.c
index 139d27c..436dd4e 100644 (file)
--- a/src/vppinfra/tw_timer_template.c
+++ b/src/vppinfra/tw_timer_template.c
@@ -170,13 +170,14 @@ void TW (tw_timer_stop) (TWT (tw_timer_wheel) * tw, u32 handle)
 void
 TW (tw_timer_wheel_init) (TWT (tw_timer_wheel) * tw,
                          void *expired_timer_callback,
-                         f64 timer_interval_in_seconds)
+                         f64 timer_interval_in_seconds, u32 max_expirations)
 {
   int ring, slot;
   tw_timer_wheel_slot_t *ts;
   TWT (tw_timer) * t;
   memset (tw, 0, sizeof (*tw));
   tw->expired_timer_callback = expired_timer_callback;
+  tw->max_expirations = max_expirations;
   if (timer_interval_in_seconds == 0.0)
     {
       clib_warning ("timer interval is zero");
@@ -258,7 +259,6 @@ u32 TW (tw_timer_expire_timers) (TWT (tw_timer_wheel) * tw, f64 now)
 
   /* Remember when we ran, compute next runtime */
   tw->next_run_time = (now + tw->timer_interval);
-  tw->last_run_time = now;
 
   total_nexpirations = 0;
   for (i = 0; i < nticks; i++)
@@ -332,8 +332,12 @@ u32 TW (tw_timer_expire_timers) (TWT (tw_timer_wheel) * tw, f64 now)
        }
       tw->current_index[TW_TIMER_RING_FAST]++;
       tw->current_tick++;
+
+      if (total_nexpirations >= tw->max_expirations)
+       break;
     }
 
+  tw->last_run_time += i * tw->ticks_per_second;
   return total_nexpirations;
 }
 

diff --git a/src/vppinfra/tw_timer_template.h b/src/vppinfra/tw_timer_template.h
index 2e41bca..6b61e42 100644 (file)
--- a/src/vppinfra/tw_timer_template.h
+++ b/src/vppinfra/tw_timer_template.h
@@ -175,6 +175,9 @@ typedef struct
 
   /** vector of expired timers */
   u32 *expired_timer_handles;
+
+  /** maximum expirations */
+  u32 max_expirations;
 } TWT (tw_timer_wheel);
 
 u32 TW (tw_timer_start) (TWT (tw_timer_wheel) * tw,
@@ -184,7 +187,7 @@ void TW (tw_timer_stop) (TWT (tw_timer_wheel) * tw, u32 handle);
 
 void TW (tw_timer_wheel_init) (TWT (tw_timer_wheel) * tw,
                               void *expired_timer_callback,
-                              f64 timer_interval);
+                              f64 timer_interval, u32 max_expirations);
 
 void TW (tw_timer_wheel_free) (TWT (tw_timer_wheel) * tw);