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@@ -23,6 +23,14 @@
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#define SCHED_Q_LOW_WATER 16384
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#define SCHED_Q_HIGH_WATER (2 * SCHED_Q_LOW_WATER)
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+/*
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+ * Maximum cells to flush in a single call to channel_flush_some_cells();
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+ * setting this low means more calls, but too high and we could overshoot
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+ * SCHED_Q_HIGH_WATER.
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+ */
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+
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+#define SCHED_MAX_FLUSH_CELLS 16
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+
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/*
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* Write scheduling works by keeping track of which channels can
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* accept cells, and have cells to write. From the scheduler's perspective,
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@@ -100,7 +108,7 @@
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* is reserved for our use.
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*/
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-/* List of channels that can write and have cells (pending work) */
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+/* Pqueue of channels that can write and have cells (pending work) */
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static smartlist_t *channels_pending = NULL;
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/*
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@@ -125,7 +133,7 @@ static time_t queue_heuristic_timestamp = 0;
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/* Scheduler static function declarations */
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-static int scheduler_compare_channels(const void **c1_v, const void **c2_v);
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+static int scheduler_compare_channels(const void *c1_v, const void *c2_v);
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static void scheduler_evt_callback(evutil_socket_t fd,
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short events, void *arg);
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static int scheduler_more_work(void);
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@@ -162,7 +170,7 @@ scheduler_free_all(void)
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*/
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static int
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-scheduler_compare_channels(const void **c1_v, const void **c2_v)
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+scheduler_compare_channels(const void *c1_v, const void *c2_v)
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{
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channel_t *c1 = NULL, *c2 = NULL;
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/* These are a workaround for -Wbad-function-cast throwing a fit */
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@@ -172,8 +180,8 @@ scheduler_compare_channels(const void **c1_v, const void **c2_v)
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tor_assert(c1_v);
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tor_assert(c2_v);
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- c1 = (channel_t *)(*c1_v);
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- c2 = (channel_t *)(*c2_v);
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+ c1 = (channel_t *)(c1_v);
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+ c2 = (channel_t *)(c2_v);
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tor_assert(c1);
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tor_assert(c2);
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@@ -241,7 +249,10 @@ scheduler_channel_doesnt_want_writes(channel_t *chan)
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* the other lists. It can't write any more, so it goes to
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* channels_waiting_to_write.
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*/
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- smartlist_remove(channels_pending, chan);
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+ smartlist_pqueue_remove(channels_pending,
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+ scheduler_compare_channels,
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+ STRUCT_OFFSET(channel_t, sched_heap_idx),
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+ chan);
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chan->scheduler_state = SCHED_CHAN_WAITING_TO_WRITE;
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log_debug(LD_SCHED,
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"Channel " U64_FORMAT " at %p went from pending "
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@@ -280,7 +291,10 @@ scheduler_channel_has_waiting_cells(channel_t *chan)
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* channels_pending.
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*/
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chan->scheduler_state = SCHED_CHAN_PENDING;
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- smartlist_add(channels_pending, chan);
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+ smartlist_pqueue_add(channels_pending,
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+ scheduler_compare_channels,
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+ STRUCT_OFFSET(channel_t, sched_heap_idx),
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+ chan);
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log_debug(LD_SCHED,
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"Channel " U64_FORMAT " at %p went from waiting_for_cells "
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"to pending",
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@@ -353,7 +367,10 @@ scheduler_release_channel(channel_t *chan)
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tor_assert(channels_pending);
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if (chan->scheduler_state == SCHED_CHAN_PENDING) {
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- smartlist_remove(channels_pending, chan);
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+ smartlist_pqueue_remove(channels_pending,
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+ scheduler_compare_channels,
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+ STRUCT_OFFSET(channel_t, sched_heap_idx),
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+ chan);
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}
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chan->scheduler_state = SCHED_CHAN_IDLE;
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@@ -364,10 +381,11 @@ scheduler_release_channel(channel_t *chan)
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void
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scheduler_run(void)
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{
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- smartlist_t *tmp = NULL;
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int n_cells, n_chans_before, n_chans_after;
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uint64_t q_len_before, q_heur_before, q_len_after, q_heur_after;
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ssize_t flushed, flushed_this_time;
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+ smartlist_t *to_readd = NULL;
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+ channel_t *chan = NULL;
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log_debug(LD_SCHED, "We have a chance to run the scheduler");
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@@ -375,61 +393,118 @@ scheduler_run(void)
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n_chans_before = smartlist_len(channels_pending);
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q_len_before = channel_get_global_queue_estimate();
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q_heur_before = scheduler_get_queue_heuristic();
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- tmp = channels_pending;
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- channels_pending = smartlist_new();
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-
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- /*
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- * UGLY HACK: sort the list on each invocation
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- *
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- * TODO smarter data structures
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- */
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- smartlist_sort(tmp, scheduler_compare_channels);
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-
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- SMARTLIST_FOREACH_BEGIN(tmp, channel_t *, chan) {
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- if (scheduler_get_queue_heuristic() <= SCHED_Q_HIGH_WATER) {
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- n_cells = channel_num_cells_writeable(chan);
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- if (n_cells > 0) {
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- log_debug(LD_SCHED,
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- "Scheduler saw pending channel " U64_FORMAT " at %p with "
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- "%d cells writeable",
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- U64_PRINTF_ARG(chan->global_identifier), chan, n_cells);
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-
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- flushed = 0;
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- while (flushed < n_cells) {
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- flushed_this_time =
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- channel_flush_some_cells(chan, n_cells - flushed);
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- if (flushed_this_time <= 0) break;
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- flushed += flushed_this_time;
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- }
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- if (flushed < n_cells) {
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- /* We ran out of cells to flush */
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- chan->scheduler_state = SCHED_CHAN_WAITING_FOR_CELLS;
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- } else {
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- /* TODO get this right */
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- }
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+ while (scheduler_get_queue_heuristic() <= SCHED_Q_HIGH_WATER &&
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+ smartlist_len(channels_pending) > 0) {
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+ /* Pop off a channel */
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+ chan = smartlist_pqueue_pop(channels_pending,
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+ scheduler_compare_channels,
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+ STRUCT_OFFSET(channel_t, sched_heap_idx));
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+ tor_assert(chan);
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+
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+ /* Figure out how many cells we can write */
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+ n_cells = channel_num_cells_writeable(chan);
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+ if (n_cells > 0) {
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+ log_debug(LD_SCHED,
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+ "Scheduler saw pending channel " U64_FORMAT " at %p with "
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+ "%d cells writeable",
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+ U64_PRINTF_ARG(chan->global_identifier), chan, n_cells);
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+
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+ flushed = 0;
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+ while (flushed < n_cells &&
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+ scheduler_get_queue_heuristic() <= SCHED_Q_HIGH_WATER) {
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+ flushed_this_time =
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+ channel_flush_some_cells(chan,
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+ MIN(SCHED_MAX_FLUSH_CELLS,
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+ n_cells - flushed));
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+ if (flushed_this_time <= 0) break;
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+ flushed += flushed_this_time;
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+ }
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+ if (flushed < n_cells) {
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+ /* We ran out of cells to flush */
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+ chan->scheduler_state = SCHED_CHAN_WAITING_FOR_CELLS;
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log_debug(LD_SCHED,
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- "Scheduler flushed %d cells onto pending channel "
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- U64_FORMAT " at %p",
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- (int)flushed, U64_PRINTF_ARG(chan->global_identifier),
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+ "Channel " U64_FORMAT " at %p "
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+ "entered waiting_for_cells from pending",
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+ U64_PRINTF_ARG(chan->global_identifier),
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chan);
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} else {
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- log_info(LD_SCHED,
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- "Scheduler saw pending channel " U64_FORMAT " at %p with "
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- "no cells writeable",
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- U64_PRINTF_ARG(chan->global_identifier), chan);
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- /* Put it back to WAITING_TO_WRITE */
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- chan->scheduler_state = SCHED_CHAN_WAITING_TO_WRITE;
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+ /* The channel may still have some cells */
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+ if (channel_more_to_flush(chan)) {
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+ /* The channel goes to either pending or waiting_to_write */
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+ if (channel_num_cells_writeable(chan) > 0) {
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+ /* Add it back to pending later */
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+ if (!to_readd) to_readd = smartlist_new();
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+ smartlist_add(to_readd, chan);
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+ log_debug(LD_SCHED,
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+ "Channel " U64_FORMAT " at %p "
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+ "is still pending",
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+ U64_PRINTF_ARG(chan->global_identifier),
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+ chan);
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+ } else {
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+ /* It's waiting to be able to write more */
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+ chan->scheduler_state = SCHED_CHAN_WAITING_TO_WRITE;
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+ log_debug(LD_SCHED,
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+ "Channel " U64_FORMAT " at %p "
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+ "entered waiting_to_write from pending",
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+ U64_PRINTF_ARG(chan->global_identifier),
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+ chan);
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+ }
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+ } else {
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+ /* No cells left; it can go to idle or waiting_for_cells */
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+ if (channel_num_cells_writeable(chan) > 0) {
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+ /*
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+ * It can still accept writes, so it goes to
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+ * waiting_for_cells
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+ */
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+ chan->scheduler_state = SCHED_CHAN_WAITING_FOR_CELLS;
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+ log_debug(LD_SCHED,
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+ "Channel " U64_FORMAT " at %p "
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+ "entered waiting_for_cells from pending",
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+ U64_PRINTF_ARG(chan->global_identifier),
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+ chan);
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+ } else {
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+ /*
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+ * We exactly filled up the output queue with all available
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+ * cells; go to idle.
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+ */
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+ chan->scheduler_state = SCHED_CHAN_IDLE;
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+ log_debug(LD_SCHED,
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+ "Channel " U64_FORMAT " at %p "
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+ "become idle from pending",
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+ U64_PRINTF_ARG(chan->global_identifier),
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+ chan);
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+ }
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+ }
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}
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+
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+ log_debug(LD_SCHED,
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+ "Scheduler flushed %d cells onto pending channel "
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+ U64_FORMAT " at %p",
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+ (int)flushed, U64_PRINTF_ARG(chan->global_identifier),
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+ chan);
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} else {
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- /* Not getting it this round; put it back on the list */
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- smartlist_add(channels_pending, chan);
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- /* It states in SCHED_CHAN_PENDING */
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+ log_info(LD_SCHED,
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+ "Scheduler saw pending channel " U64_FORMAT " at %p with "
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+ "no cells writeable",
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+ U64_PRINTF_ARG(chan->global_identifier), chan);
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+ /* Put it back to WAITING_TO_WRITE */
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+ chan->scheduler_state = SCHED_CHAN_WAITING_TO_WRITE;
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}
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- } SMARTLIST_FOREACH_END(chan);
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+ }
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- smartlist_free(tmp);
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+ /* Readd any channels we need to */
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+ if (to_readd) {
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+ SMARTLIST_FOREACH_BEGIN(to_readd, channel_t *, chan) {
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+ chan->scheduler_state = SCHED_CHAN_PENDING;
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+ smartlist_pqueue_add(channels_pending,
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+ scheduler_compare_channels,
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+ STRUCT_OFFSET(channel_t, sched_heap_idx),
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+ chan);
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+ } SMARTLIST_FOREACH_END(chan);
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+ smartlist_free(to_readd);
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+ }
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n_chans_after = smartlist_len(channels_pending);
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q_len_after = channel_get_global_queue_estimate();
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@@ -473,7 +548,10 @@ scheduler_channel_wants_writes(channel_t *chan)
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/*
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* It can write now, so it goes to channels_pending.
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*/
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- smartlist_add(channels_pending, chan);
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+ smartlist_pqueue_add(channels_pending,
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+ scheduler_compare_channels,
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+ STRUCT_OFFSET(channel_t, sched_heap_idx),
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+ chan);
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chan->scheduler_state = SCHED_CHAN_PENDING;
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log_debug(LD_SCHED,
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"Channel " U64_FORMAT " at %p went from waiting_to_write "
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