Make queue thresholds and flush size for global scheduler into config options

src/or/config.c

@@ -367,6 +367,9 @@ static config_var_t option_vars_[] = {
   V(ServerDNSSearchDomains,      BOOL,     "0"),
   V(ServerDNSTestAddresses,      CSV,
       "www.google.com,www.mit.edu,www.yahoo.com,www.slashdot.org"),
+  V(SchedulerLowWaterMark,       MEMUNIT,  "16 kB"),
+  V(SchedulerHighWaterMark,      MEMUNIT,  "32 kB"),
+  V(SchedulerMaxFlushCells,      UINT,     "16"),
   V(ShutdownWaitLength,          INTERVAL, "30 seconds"),
   V(SocksListenAddress,          LINELIST, NULL),
   V(SocksPolicy,                 LINELIST, NULL),
@@ -1522,6 +1525,25 @@ options_act(const or_options_t *old_options)
     return -1;
   }
 
+  /* Set up scheduler thresholds */
+  if (options->SchedulerLowWaterMark > 0 &&
+      options->SchedulerHighWaterMark > options->SchedulerLowWaterMark) {
+    scheduler_set_watermarks(options->SchedulerLowWaterMark,
+                             options->SchedulerHighWaterMark,
+                             (options->SchedulerMaxFlushCells > 0) ?
+                              options->SchedulerMaxFlushCells : 16);
+  } else {
+    if (options->SchedulerLowWaterMark == 0) {
+      log_warn(LD_GENERAL, "Bad SchedulerLowWaterMark option");
+    }
+
+    if (options->SchedulerHighWaterMark <= options->SchedulerLowWaterMark) {
+      log_warn(LD_GENERAL, "Bad SchedulerHighWaterMark option");
+    }
+
+    return -1;
+  }
+
   /* Set up accounting */
   if (accounting_parse_options(options, 0)<0) {
     log_warn(LD_CONFIG,"Error in accounting options");

src/or/or.h

@@ -4229,6 +4229,19 @@ typedef struct {
 
   /** Should we send the timestamps that pre-023 hidden services want? */
   int Support022HiddenServices;
+
+  /** Low-water mark for global scheduler - start sending when estimated
+   * queued size falls below this threshold.
+   */
+  uint32_t SchedulerLowWaterMark;
+  /** High-water mark for global scheduler - stop sending when estimated
+   * queued size exceeds this threshold.
+   */
+  uint32_t SchedulerHighWaterMark;
+  /** Flush size for global scheduler - flush this many cells at a time
+   * when sending.
+   */
+  unsigned int SchedulerMaxFlushCells;
 } or_options_t;
 
 /** Persistent state for an onion router, as saved to disk. */

src/or/scheduler.c

@@ -21,16 +21,20 @@
 #include <event.h>
 #endif
 
-#define SCHED_Q_LOW_WATER 16384
-#define SCHED_Q_HIGH_WATER (2 * SCHED_Q_LOW_WATER)
+/*
+ * Scheduler high/low watermarks
+ */
+
+static uint32_t sched_q_low_water = 16384;
+static uint32_t sched_q_high_water = 32768;
 
 /*
  * Maximum cells to flush in a single call to channel_flush_some_cells();
  * setting this low means more calls, but too high and we could overshoot
- * SCHED_Q_HIGH_WATER.
+ * sched_q_high_water.
  */
 
-#define SCHED_MAX_FLUSH_CELLS 16
+static uint32_t sched_max_flush_cells = 16;
 
 /*
  * Write scheduling works by keeping track of which channels can
@@ -343,7 +347,7 @@ scheduler_more_work(void)
 {
   tor_assert(channels_pending);
 
-  return ((scheduler_get_queue_heuristic() < SCHED_Q_LOW_WATER) &&
+  return ((scheduler_get_queue_heuristic() < sched_q_low_water) &&
           ((smartlist_len(channels_pending) > 0))) ? 1 : 0;
 }
 
@@ -387,12 +391,12 @@ scheduler_run, (void))
 
   log_debug(LD_SCHED, "We have a chance to run the scheduler");
 
-  if (scheduler_get_queue_heuristic() < SCHED_Q_LOW_WATER) {
+  if (scheduler_get_queue_heuristic() < sched_q_low_water) {
     n_chans_before = smartlist_len(channels_pending);
     q_len_before = channel_get_global_queue_estimate();
     q_heur_before = scheduler_get_queue_heuristic();
 
-    while (scheduler_get_queue_heuristic() <= SCHED_Q_HIGH_WATER &&
+    while (scheduler_get_queue_heuristic() <= sched_q_high_water &&
            smartlist_len(channels_pending) > 0) {
       /* Pop off a channel */
       chan = smartlist_pqueue_pop(channels_pending,
@@ -410,10 +414,10 @@ scheduler_run, (void))
 
         flushed = 0;
         while (flushed < n_cells &&
-               scheduler_get_queue_heuristic() <= SCHED_Q_HIGH_WATER) {
+               scheduler_get_queue_heuristic() <= sched_q_high_water) {
           flushed_this_time =
             channel_flush_some_cells(chan,
-                                     MIN(SCHED_MAX_FLUSH_CELLS,
+                                     MIN(sched_max_flush_cells,
                                          n_cells - flushed));
           if (flushed_this_time <= 0) break;
           flushed += flushed_this_time;
@@ -686,3 +690,19 @@ scheduler_update_queue_heuristic(time_t now)
   /* else no update needed, or time went backward */
 }
 
+/**
+ * Set scheduler watermarks and flush size
+ */
+
+void
+scheduler_set_watermarks(uint32_t lo, uint32_t hi, uint32_t max_flush)
+{
+  /* Sanity assertions - caller should ensure these are true */
+  tor_assert(lo > 0);
+  tor_assert(hi > lo);
+  tor_assert(max_flush > 0);
+
+  sched_q_low_water = lo;
+  sched_q_high_water = hi;
+  sched_max_flush_cells = max_flush;
+}

src/or/scheduler.h

@@ -34,6 +34,9 @@ void scheduler_adjust_queue_size(channel_t *chan, char dir, uint64_t adj);
 /* Notify scheduler that a channel's queue position may have changed */
 void scheduler_touch_channel(channel_t *chan);
 
+/* Adjust the watermarks from config file*/
+void scheduler_set_watermarks(uint32_t lo, uint32_t hi, uint32_t max_flush);
+
 /* Things only scheduler.c and its test suite should see */
 
 #ifdef SCHEDULER_PRIVATE_