alsa: automatically decrease watermark after a time of stability

4 files changed, 240 insertions, 83 deletions

diff --git a/src/modules/alsa/alsa-sink.c b/src/modules/alsa/alsa-sink.c
index b99ed782..07d53880 100644
--- a/src/modules/alsa/alsa-sink.c
+++ b/src/modules/alsa/alsa-sink.c
@@ -62,14 +62,21 @@
 /* #define DEBUG_TIMING */
 
 #define DEFAULT_DEVICE "default"
-#define DEFAULT_TSCHED_BUFFER_USEC (2*PA_USEC_PER_SEC)            /* 2s   -- Overall buffer size */
-#define DEFAULT_TSCHED_WATERMARK_USEC (20*PA_USEC_PER_MSEC)       /* 20ms -- Fill up when only this much is left in the buffer */
-#define TSCHED_WATERMARK_STEP_USEC (10*PA_USEC_PER_MSEC)          /* 10ms -- On underrun, increase watermark by this */
-#define TSCHED_MIN_SLEEP_USEC (10*PA_USEC_PER_MSEC)               /* 10ms -- Sleep at least 10ms on each iteration */
-#define TSCHED_MIN_WAKEUP_USEC (4*PA_USEC_PER_MSEC)               /* 4ms  -- Wakeup at least this long before the buffer runs empty*/
 
-#define SMOOTHER_MIN_INTERVAL (2*PA_USEC_PER_MSEC)                /* 2ms -- min smoother update interval */
-#define SMOOTHER_MAX_INTERVAL (200*PA_USEC_PER_MSEC)              /* 200ms -- max smoother update inteval */
+#define DEFAULT_TSCHED_BUFFER_USEC (2*PA_USEC_PER_SEC)             /* 2s    -- Overall buffer size */
+#define DEFAULT_TSCHED_WATERMARK_USEC (20*PA_USEC_PER_MSEC)        /* 20ms  -- Fill up when only this much is left in the buffer */
+
+#define TSCHED_WATERMARK_INC_STEP_USEC (10*PA_USEC_PER_MSEC)       /* 10ms  -- On underrun, increase watermark by this */
+#define TSCHED_WATERMARK_DEC_STEP_USEC (5*PA_USEC_PER_MSEC)        /* 5ms   -- When everything's great, decrease watermark by this */
+#define TSCHED_WATERMARK_VERIFY_AFTER_USEC (20*PA_USEC_PER_SEC)    /* 20s   -- How long after a drop out recheck if things are good now */
+#define TSCHED_WATERMARK_INC_THRESHOLD_USEC (1*PA_USEC_PER_MSEC)   /* 3ms   -- If the buffer level ever below this theshold, increase the watermark */
+#define TSCHED_WATERMARK_DEC_THRESHOLD_USEC (100*PA_USEC_PER_MSEC) /* 100ms -- If the buffer level didn't drop below this theshold in the verification time, decrease the watermark */
+
+#define TSCHED_MIN_SLEEP_USEC (10*PA_USEC_PER_MSEC)                /* 10ms  -- Sleep at least 10ms on each iteration */
+#define TSCHED_MIN_WAKEUP_USEC (4*PA_USEC_PER_MSEC)                /* 4ms   -- Wakeup at least this long before the buffer runs empty*/
+
+#define SMOOTHER_MIN_INTERVAL (2*PA_USEC_PER_MSEC)                 /* 2ms   -- min smoother update interval */
+#define SMOOTHER_MAX_INTERVAL (200*PA_USEC_PER_MSEC)               /* 200ms -- max smoother update inteval */
 
 #define VOLUME_ACCURACY (PA_VOLUME_NORM/100)  /* don't require volume adjustments to be perfectly correct. don't necessarily extend granularity in software unless the differences get greater than this level */
 
@@ -99,7 +106,12 @@ struct userdata {
         hwbuf_unused,
         min_sleep,
         min_wakeup,
-        watermark_step;
+        watermark_inc_step,
+        watermark_dec_step,
+        watermark_inc_threshold,
+        watermark_dec_threshold;
+
+    pa_usec_t watermark_dec_not_before;
 
     unsigned nfragments;
     pa_memchunk memchunk;
@@ -248,6 +260,7 @@ static void fix_min_sleep_wakeup(struct userdata *u) {
     size_t max_use, max_use_2;
 
     pa_assert(u);
+    pa_assert(u->use_tsched);
 
     max_use = u->hwbuf_size - u->hwbuf_unused;
     max_use_2 = pa_frame_align(max_use/2, &u->sink->sample_spec);
@@ -262,6 +275,7 @@ static void fix_min_sleep_wakeup(struct userdata *u) {
 static void fix_tsched_watermark(struct userdata *u) {
     size_t max_use;
     pa_assert(u);
+    pa_assert(u->use_tsched);
 
     max_use = u->hwbuf_size - u->hwbuf_unused;
 
@@ -272,7 +286,7 @@ static void fix_tsched_watermark(struct userdata *u) {
         u->tsched_watermark = u->min_wakeup;
 }
 
-static void adjust_after_underrun(struct userdata *u) {
+static void increase_watermark(struct userdata *u) {
     size_t old_watermark;
     pa_usec_t old_min_latency, new_min_latency;
 
@@ -281,31 +295,64 @@ static void adjust_after_underrun(struct userdata *u) {
 
     /* First, just try to increase the watermark */
     old_watermark = u->tsched_watermark;
-    u->tsched_watermark = PA_MIN(u->tsched_watermark * 2, u->tsched_watermark + u->watermark_step);
+    u->tsched_watermark = PA_MIN(u->tsched_watermark * 2, u->tsched_watermark + u->watermark_inc_step);
     fix_tsched_watermark(u);
 
     if (old_watermark != u->tsched_watermark) {
-        pa_log_notice("Increasing wakeup watermark to %0.2f ms",
-                      (double) pa_bytes_to_usec(u->tsched_watermark, &u->sink->sample_spec) / PA_USEC_PER_MSEC);
+        pa_log_info("Increasing wakeup watermark to %0.2f ms",
+                    (double) pa_bytes_to_usec(u->tsched_watermark, &u->sink->sample_spec) / PA_USEC_PER_MSEC);
         return;
     }
 
     /* Hmm, we cannot increase the watermark any further, hence let's raise the latency */
     old_min_latency = u->sink->thread_info.min_latency;
-    new_min_latency = PA_MIN(old_min_latency * 2, old_min_latency + TSCHED_WATERMARK_STEP_USEC);
+    new_min_latency = PA_MIN(old_min_latency * 2, old_min_latency + TSCHED_WATERMARK_INC_STEP_USEC);
     new_min_latency = PA_MIN(new_min_latency, u->sink->thread_info.max_latency);
 
     if (old_min_latency != new_min_latency) {
-        pa_log_notice("Increasing minimal latency to %0.2f ms",
-                      (double) new_min_latency / PA_USEC_PER_MSEC);
+        pa_log_info("Increasing minimal latency to %0.2f ms",
+                    (double) new_min_latency / PA_USEC_PER_MSEC);
 
         pa_sink_set_latency_range_within_thread(u->sink, new_min_latency, u->sink->thread_info.max_latency);
-        return;
     }
 
     /* When we reach this we're officialy fucked! */
 }
 
+static void decrease_watermark(struct userdata *u) {
+    size_t old_watermark;
+    pa_usec_t now;
+
+    pa_assert(u);
+    pa_assert(u->use_tsched);
+
+    now = pa_rtclock_now();
+
+    if (u->watermark_dec_not_before <= 0)
+        goto restart;
+
+    if (u->watermark_dec_not_before > now)
+        return;
+
+    old_watermark = u->tsched_watermark;
+
+    if (u->tsched_watermark < u->watermark_dec_step)
+        u->tsched_watermark = u->tsched_watermark / 2;
+    else
+        u->tsched_watermark = PA_MAX(u->tsched_watermark / 2, u->tsched_watermark - u->watermark_dec_step);
+
+    fix_tsched_watermark(u);
+
+    if (old_watermark != u->tsched_watermark)
+        pa_log_info("Decreasing wakeup watermark to %0.2f ms",
+                    (double) pa_bytes_to_usec(u->tsched_watermark, &u->sink->sample_spec) / PA_USEC_PER_MSEC);
+
+    /* We don't change the latency range*/
+
+restart:
+    u->watermark_dec_not_before = now + TSCHED_WATERMARK_VERIFY_AFTER_USEC;
+}
+
 static void hw_sleep_time(struct userdata *u, pa_usec_t *sleep_usec, pa_usec_t*process_usec) {
     pa_usec_t usec, wm;
 
@@ -313,6 +360,7 @@ static void hw_sleep_time(struct userdata *u, pa_usec_t *sleep_usec, pa_usec_t*p
     pa_assert(process_usec);
 
     pa_assert(u);
+    pa_assert(u->use_tsched);
 
     usec = pa_sink_get_requested_latency_within_thread(u->sink);
 
@@ -360,7 +408,7 @@ static int try_recover(struct userdata *u, const char *call, int err) {
     return 0;
 }
 
-static size_t check_left_to_play(struct userdata *u, size_t n_bytes) {
+static size_t check_left_to_play(struct userdata *u, size_t n_bytes, pa_bool_t on_timeout) {
     size_t left_to_play;
 
     /* We use <= instead of < for this check here because an underrun
@@ -368,34 +416,55 @@ static size_t check_left_to_play(struct userdata *u, size_t n_bytes) {
      * it is removed from the buffer. This is particularly important
      * when block transfer is used. */
 
-    if (n_bytes <= u->hwbuf_size) {
+    if (n_bytes <= u->hwbuf_size)
         left_to_play = u->hwbuf_size - n_bytes;
+    else {
+
+        /* We got a dropout. What a mess! */
+        left_to_play = 0;
 
 #ifdef DEBUG_TIMING
-        pa_log_debug("%0.2f ms left to play", (double) pa_bytes_to_usec(left_to_play, &u->sink->sample_spec) / PA_USEC_PER_MSEC);
+        PA_DEBUG_TRAP;
 #endif
 
-    } else {
-        left_to_play = 0;
+        if (!u->first && !u->after_rewind)
+            if (pa_log_ratelimit())
+                pa_log_info("Underrun!");
+    }
 
 #ifdef DEBUG_TIMING
-        PA_DEBUG_TRAP;
+    pa_log_debug("%0.2f ms left to play; inc threshold = %0.2f ms; dec threshold = %0.2f ms",
+                 (double) pa_bytes_to_usec(left_to_play, &u->sink->sample_spec) / PA_USEC_PER_MSEC,
+                 (double) pa_bytes_to_usec(u->watermark_inc_threshold, &u->sink->sample_spec) / PA_USEC_PER_MSEC,
+                 (double) pa_bytes_to_usec(u->watermark_dec_threshold, &u->sink->sample_spec) / PA_USEC_PER_MSEC);
 #endif
 
+    if (u->use_tsched) {
+        pa_bool_t reset_not_before = TRUE;
+
         if (!u->first && !u->after_rewind) {
+            if (left_to_play < u->watermark_inc_threshold)
+                increase_watermark(u);
+            else if (left_to_play > u->watermark_dec_threshold) {
+                reset_not_before = FALSE;
 
-            if (pa_log_ratelimit())
-                pa_log_info("Underrun!");
+                /* We decrease the watermark only if have actually
+                 * been woken up by a timeout. If something else woke
+                 * us up it's too easy to fulfill the deadlines... */
 
-            if (u->use_tsched)
-                adjust_after_underrun(u);
+                if (on_timeout)
+                    decrease_watermark(u);
+            }
         }
+
+        if (reset_not_before)
+            u->watermark_dec_not_before = 0;
     }
 
     return left_to_play;
 }
 
-static int mmap_write(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled) {
+static int mmap_write(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled, pa_bool_t on_timeout) {
     pa_bool_t work_done = TRUE;
     pa_usec_t max_sleep_usec = 0, process_usec = 0;
     size_t left_to_play;
@@ -430,7 +499,8 @@ static int mmap_write(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polle
         pa_log_debug("avail: %lu", (unsigned long) n_bytes);
 #endif
 
-        left_to_play = check_left_to_play(u, n_bytes);
+        left_to_play = check_left_to_play(u, n_bytes, on_timeout);
+        on_timeout = FALSE;
 
         if (u->use_tsched)
 
@@ -565,7 +635,7 @@ static int mmap_write(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polle
     return work_done ? 1 : 0;
 }
 
-static int unix_write(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled) {
+static int unix_write(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled, pa_bool_t on_timeout) {
     pa_bool_t work_done = FALSE;
     pa_usec_t max_sleep_usec = 0, process_usec = 0;
     size_t left_to_play;
@@ -591,7 +661,8 @@ static int unix_write(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polle
         }
 
         n_bytes = (size_t) n * u->frame_size;
-        left_to_play = check_left_to_play(u, n_bytes);
+        left_to_play = check_left_to_play(u, n_bytes, on_timeout);
+        on_timeout = FALSE;
 
         if (u->use_tsched)
 
@@ -1278,15 +1349,16 @@ static void thread_func(void *userdata) {
         if (PA_SINK_IS_OPENED(u->sink->thread_info.state)) {
             int work_done;
             pa_usec_t sleep_usec = 0;
+            pa_bool_t on_timeout = pa_rtpoll_timer_elapsed(u->rtpoll);
 
             if (PA_UNLIKELY(u->sink->thread_info.rewind_requested))
                 if (process_rewind(u) < 0)
                         goto fail;
 
             if (u->use_mmap)
-                work_done = mmap_write(u, &sleep_usec, revents & POLLOUT);
+                work_done = mmap_write(u, &sleep_usec, revents & POLLOUT, on_timeout);
             else
-                work_done = unix_write(u, &sleep_usec, revents & POLLOUT);
+                work_done = unix_write(u, &sleep_usec, revents & POLLOUT, on_timeout);
 
             if (work_done < 0)
                 goto fail;
@@ -1787,7 +1859,6 @@ pa_sink *pa_alsa_sink_new(pa_module *m, pa_modargs *ma, const char*driver, pa_ca
     u->fragment_size = frag_size = (uint32_t) (period_frames * frame_size);
     u->nfragments = nfrags;
     u->hwbuf_size = u->fragment_size * nfrags;
-    u->tsched_watermark = pa_usec_to_bytes_round_up(pa_bytes_to_usec_round_up(tsched_watermark, &requested_ss), &u->sink->sample_spec);
     pa_cvolume_mute(&u->hardware_volume, u->sink->sample_spec.channels);
 
     pa_log_info("Using %u fragments of size %lu bytes, buffer time is %0.2fms",
@@ -1798,7 +1869,13 @@ pa_sink *pa_alsa_sink_new(pa_module *m, pa_modargs *ma, const char*driver, pa_ca
     pa_sink_set_max_rewind(u->sink, u->hwbuf_size);
 
     if (u->use_tsched) {
-        u->watermark_step = pa_usec_to_bytes(TSCHED_WATERMARK_STEP_USEC, &u->sink->sample_spec);
+        u->tsched_watermark = pa_usec_to_bytes_round_up(pa_bytes_to_usec_round_up(tsched_watermark, &requested_ss), &u->sink->sample_spec);
+
+        u->watermark_inc_step = pa_usec_to_bytes(TSCHED_WATERMARK_INC_STEP_USEC, &u->sink->sample_spec);
+        u->watermark_dec_step = pa_usec_to_bytes(TSCHED_WATERMARK_DEC_STEP_USEC, &u->sink->sample_spec);
+
+        u->watermark_inc_threshold = pa_usec_to_bytes_round_up(TSCHED_WATERMARK_INC_THRESHOLD_USEC, &u->sink->sample_spec);
+        u->watermark_dec_threshold = pa_usec_to_bytes_round_up(TSCHED_WATERMARK_DEC_THRESHOLD_USEC, &u->sink->sample_spec);
 
         fix_min_sleep_wakeup(u);
         fix_tsched_watermark(u);
@@ -1812,6 +1889,7 @@ pa_sink *pa_alsa_sink_new(pa_module *m, pa_modargs *ma, const char*driver, pa_ca
     } else
         pa_sink_set_fixed_latency(u->sink, pa_bytes_to_usec(u->hwbuf_size, &ss));
 
+
     reserve_update(u);
 
     if (update_sw_params(u) < 0)
diff --git a/src/modules/alsa/alsa-source.c b/src/modules/alsa/alsa-source.c
index 336027a2..165b2e3b 100644
--- a/src/modules/alsa/alsa-source.c
+++ b/src/modules/alsa/alsa-source.c
@@ -59,14 +59,22 @@
 /* #define DEBUG_TIMING */
 
 #define DEFAULT_DEVICE "default"
-#define DEFAULT_TSCHED_BUFFER_USEC (2*PA_USEC_PER_SEC)       /* 2s */
-#define DEFAULT_TSCHED_WATERMARK_USEC (20*PA_USEC_PER_MSEC)  /* 20ms */
-#define TSCHED_WATERMARK_STEP_USEC (10*PA_USEC_PER_MSEC)     /* 10ms */
-#define TSCHED_MIN_SLEEP_USEC (10*PA_USEC_PER_MSEC)          /* 10ms */
-#define TSCHED_MIN_WAKEUP_USEC (4*PA_USEC_PER_MSEC)          /* 4ms */
 
-#define SMOOTHER_MIN_INTERVAL (2*PA_USEC_PER_MSEC)           /* 2ms */
-#define SMOOTHER_MAX_INTERVAL (200*PA_USEC_PER_MSEC)         /* 200ms */
+#define DEFAULT_TSCHED_BUFFER_USEC (2*PA_USEC_PER_SEC)             /* 2s */
+#define DEFAULT_TSCHED_WATERMARK_USEC (20*PA_USEC_PER_MSEC)        /* 20ms */
+
+#define TSCHED_WATERMARK_INC_STEP_USEC (10*PA_USEC_PER_MSEC)       /* 10ms  */
+#define TSCHED_WATERMARK_DEC_STEP_USEC (5*PA_USEC_PER_MSEC)        /* 5ms */
+#define TSCHED_WATERMARK_VERIFY_AFTER_USEC (20*PA_USEC_PER_SEC)    /* 20s */
+#define TSCHED_WATERMARK_INC_THRESHOLD_USEC (1*PA_USEC_PER_MSEC)   /* 3ms */
+#define TSCHED_WATERMARK_DEC_THRESHOLD_USEC (100*PA_USEC_PER_MSEC) /* 100ms */
+#define TSCHED_WATERMARK_STEP_USEC (10*PA_USEC_PER_MSEC)           /* 10ms */
+
+#define TSCHED_MIN_SLEEP_USEC (10*PA_USEC_PER_MSEC)                /* 10ms */
+#define TSCHED_MIN_WAKEUP_USEC (4*PA_USEC_PER_MSEC)                /* 4ms */
+
+#define SMOOTHER_MIN_INTERVAL (2*PA_USEC_PER_MSEC)                 /* 2ms */
+#define SMOOTHER_MAX_INTERVAL (200*PA_USEC_PER_MSEC)               /* 200ms */
 
 #define VOLUME_ACCURACY (PA_VOLUME_NORM/100)
 
@@ -96,7 +104,12 @@ struct userdata {
         hwbuf_unused,
         min_sleep,
         min_wakeup,
-        watermark_step;
+        watermark_inc_step,
+        watermark_dec_step,
+        watermark_inc_threshold,
+        watermark_dec_threshold;
+
+    pa_usec_t watermark_dec_not_before;
 
     unsigned nfragments;
 
@@ -241,6 +254,7 @@ static int reserve_monitor_init(struct userdata *u, const char *dname) {
 static void fix_min_sleep_wakeup(struct userdata *u) {
     size_t max_use, max_use_2;
     pa_assert(u);
+    pa_assert(u->use_tsched);
 
     max_use = u->hwbuf_size - u->hwbuf_unused;
     max_use_2 = pa_frame_align(max_use/2, &u->source->sample_spec);
@@ -255,6 +269,7 @@ static void fix_min_sleep_wakeup(struct userdata *u) {
 static void fix_tsched_watermark(struct userdata *u) {
     size_t max_use;
     pa_assert(u);
+    pa_assert(u->use_tsched);
 
     max_use = u->hwbuf_size - u->hwbuf_unused;
 
@@ -265,7 +280,7 @@ static void fix_tsched_watermark(struct userdata *u) {
         u->tsched_watermark = u->min_wakeup;
 }
 
-static void adjust_after_overrun(struct userdata *u) {
+static void increase_watermark(struct userdata *u) {
     size_t old_watermark;
     pa_usec_t old_min_latency, new_min_latency;
 
@@ -274,36 +289,72 @@ static void adjust_after_overrun(struct userdata *u) {
 
     /* First, just try to increase the watermark */
     old_watermark = u->tsched_watermark;
-    u->tsched_watermark = PA_MIN(u->tsched_watermark * 2, u->tsched_watermark + u->watermark_step);
-
+    u->tsched_watermark = PA_MIN(u->tsched_watermark * 2, u->tsched_watermark + u->watermark_inc_step);
     fix_tsched_watermark(u);
 
     if (old_watermark != u->tsched_watermark) {
-        pa_log_notice("Increasing wakeup watermark to %0.2f ms",
-                      (double) pa_bytes_to_usec(u->tsched_watermark, &u->source->sample_spec) / PA_USEC_PER_MSEC);
+        pa_log_info("Increasing wakeup watermark to %0.2f ms",
+                    (double) pa_bytes_to_usec(u->tsched_watermark, &u->source->sample_spec) / PA_USEC_PER_MSEC);
         return;
     }
 
     /* Hmm, we cannot increase the watermark any further, hence let's raise the latency */
     old_min_latency = u->source->thread_info.min_latency;
-    new_min_latency = PA_MIN(old_min_latency * 2, old_min_latency + TSCHED_WATERMARK_STEP_USEC);
+    new_min_latency = PA_MIN(old_min_latency * 2, old_min_latency + TSCHED_WATERMARK_INC_STEP_USEC);
     new_min_latency = PA_MIN(new_min_latency, u->source->thread_info.max_latency);
 
     if (old_min_latency != new_min_latency) {
-        pa_log_notice("Increasing minimal latency to %0.2f ms",
-                      (double) new_min_latency / PA_USEC_PER_MSEC);
+        pa_log_info("Increasing minimal latency to %0.2f ms",
+                    (double) new_min_latency / PA_USEC_PER_MSEC);
 
         pa_source_set_latency_range_within_thread(u->source, new_min_latency, u->source->thread_info.max_latency);
-        return;
     }
 
     /* When we reach this we're officialy fucked! */
 }
 
+static void decrease_watermark(struct userdata *u) {
+    size_t old_watermark;
+    pa_usec_t now;
+
+    pa_assert(u);
+    pa_assert(u->use_tsched);
+
+    now = pa_rtclock_now();
+
+    if (u->watermark_dec_not_before <= 0)
+        goto restart;
+
+    if (u->watermark_dec_not_before > now)
+        return;
+
+    old_watermark = u->tsched_watermark;
+
+    if (u->tsched_watermark < u->watermark_dec_step)
+        u->tsched_watermark = u->tsched_watermark / 2;
+    else
+        u->tsched_watermark = PA_MAX(u->tsched_watermark / 2, u->tsched_watermark - u->watermark_dec_step);
+
+    fix_tsched_watermark(u);
+
+    if (old_watermark != u->tsched_watermark)
+        pa_log_info("Decreasing wakeup watermark to %0.2f ms",
+                    (double) pa_bytes_to_usec(u->tsched_watermark, &u->source->sample_spec) / PA_USEC_PER_MSEC);
+
+    /* We don't change the latency range*/
+
+restart:
+    u->watermark_dec_not_before = now + TSCHED_WATERMARK_VERIFY_AFTER_USEC;
+}
+
 static pa_usec_t hw_sleep_time(struct userdata *u, pa_usec_t *sleep_usec, pa_usec_t*process_usec) {
     pa_usec_t wm, usec;
 
+    pa_assert(sleep_usec);
+    pa_assert(process_usec);
+
     pa_assert(u);
+    pa_assert(u->use_tsched);
 
     usec = pa_source_get_requested_latency_within_thread(u->source);
 
@@ -352,7 +403,7 @@ static int try_recover(struct userdata *u, const char *call, int err) {
     return 0;
 }
 
-static size_t check_left_to_record(struct userdata *u, size_t n_bytes) {
+static size_t check_left_to_record(struct userdata *u, size_t n_bytes, pa_bool_t on_timeout) {
     size_t left_to_record;
     size_t rec_space = u->hwbuf_size - u->hwbuf_unused;
 
@@ -361,14 +412,11 @@ static size_t check_left_to_record(struct userdata *u, size_t n_bytes) {
      * it is removed from the buffer. This is particularly important
      * when block transfer is used. */
 
-    if (n_bytes <= rec_space) {
+    if (n_bytes <= rec_space)
         left_to_record = rec_space - n_bytes;
+    else {
 
-#ifdef DEBUG_TIMING
-        pa_log_debug("%0.2f ms left to record", (double) pa_bytes_to_usec(left_to_record, &u->source->sample_spec) / PA_USEC_PER_MSEC);
-#endif
-
-    } else {
+        /* We got a dropout. What a mess! */
         left_to_record = 0;
 
 #ifdef DEBUG_TIMING
@@ -377,15 +425,36 @@ static size_t check_left_to_record(struct userdata *u, size_t n_bytes) {
 
         if (pa_log_ratelimit())
             pa_log_info("Overrun!");
+    }
 
-        if (u->use_tsched)
-            adjust_after_overrun(u);
+#ifdef DEBUG_TIMING
+    pa_log_debug("%0.2f ms left to record", (double) pa_bytes_to_usec(left_to_record, &u->source->sample_spec) / PA_USEC_PER_MSEC);
+#endif
+
+    if (u->use_tsched) {
+        pa_bool_t reset_not_before = TRUE;
+
+        if (left_to_record < u->watermark_inc_threshold)
+            increase_watermark(u);
+        else if (left_to_record > u->watermark_dec_threshold) {
+            reset_not_before = FALSE;
+
+            /* We decrease the watermark only if have actually been
+             * woken up by a timeout. If something else woke us up
+             * it's too easy to fulfill the deadlines... */
+
+            if (on_timeout)
+                decrease_watermark(u);
+        }
+
+        if (reset_not_before)
+            u->watermark_dec_not_before = 0;
     }
 
     return left_to_record;
 }
 
-static int mmap_read(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled) {
+static int mmap_read(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled, pa_bool_t on_timeout) {
     pa_bool_t work_done = FALSE;
     pa_usec_t max_sleep_usec = 0, process_usec = 0;
     size_t left_to_record;
@@ -417,7 +486,8 @@ static int mmap_read(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled
         pa_log_debug("avail: %lu", (unsigned long) n_bytes);
 #endif
 
-        left_to_record = check_left_to_record(u, n_bytes);
+        left_to_record = check_left_to_record(u, n_bytes, on_timeout);
+        on_timeout = FALSE;
 
         if (u->use_tsched)
             if (!polled &&
@@ -543,7 +613,7 @@ static int mmap_read(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled
     return work_done ? 1 : 0;
 }
 
-static int unix_read(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled) {
+static int unix_read(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled, pa_bool_t on_timeout) {
     int work_done = FALSE;
     pa_usec_t max_sleep_usec = 0, process_usec = 0;
     size_t left_to_record;
@@ -570,7 +640,8 @@ static int unix_read(struct userdata *u, pa_usec_t *sleep_usec, pa_bool_t polled
         }
 
         n_bytes = (size_t) n * u->frame_size;
-        left_to_record = check_left_to_record(u, n_bytes);
+        left_to_record = check_left_to_record(u, n_bytes, on_timeout);
+        on_timeout = FALSE;
 
         if (u->use_tsched)
             if (!polled &&
@@ -1158,11 +1229,12 @@ static void thread_func(void *userdata) {
         if (PA_SOURCE_IS_OPENED(u->source->thread_info.state)) {
             int work_done;
             pa_usec_t sleep_usec = 0;
+            pa_bool_t on_timeout = pa_rtpoll_timer_elapsed(u->rtpoll);
 
             if (u->use_mmap)
-                work_done = mmap_read(u, &sleep_usec, revents & POLLIN);
+                work_done = mmap_read(u, &sleep_usec, revents & POLLIN, on_timeout);
             else
-                work_done = unix_read(u, &sleep_usec, revents & POLLIN);
+                work_done = unix_read(u, &sleep_usec, revents & POLLIN, on_timeout);
 
             if (work_done < 0)
                 goto fail;
@@ -1632,7 +1704,6 @@ pa_source *pa_alsa_source_new(pa_module *m, pa_modargs *ma, const char*driver, p
     u->fragment_size = frag_size = (uint32_t) (period_frames * frame_size);
     u->nfragments = nfrags;
     u->hwbuf_size = u->fragment_size * nfrags;
-    u->tsched_watermark = pa_usec_to_bytes_round_up(pa_bytes_to_usec_round_up(tsched_watermark, &requested_ss), &u->source->sample_spec);
     pa_cvolume_mute(&u->hardware_volume, u->source->sample_spec.channels);
 
     pa_log_info("Using %u fragments of size %lu bytes, buffer time is %0.2fms",
@@ -1640,7 +1711,13 @@ pa_source *pa_alsa_source_new(pa_module *m, pa_modargs *ma, const char*driver, p
                 (double) pa_bytes_to_usec(u->hwbuf_size, &ss) / PA_USEC_PER_MSEC);
 
     if (u->use_tsched) {
-        u->watermark_step = pa_usec_to_bytes(TSCHED_WATERMARK_STEP_USEC, &u->source->sample_spec);
+        u->tsched_watermark = pa_usec_to_bytes_round_up(pa_bytes_to_usec_round_up(tsched_watermark, &requested_ss), &u->source->sample_spec);
+
+        u->watermark_inc_step = pa_usec_to_bytes(TSCHED_WATERMARK_INC_STEP_USEC, &u->source->sample_spec);
+        u->watermark_dec_step = pa_usec_to_bytes(TSCHED_WATERMARK_DEC_STEP_USEC, &u->source->sample_spec);
+
+        u->watermark_inc_threshold = pa_usec_to_bytes_round_up(TSCHED_WATERMARK_INC_THRESHOLD_USEC, &u->source->sample_spec);
+        u->watermark_dec_threshold = pa_usec_to_bytes_round_up(TSCHED_WATERMARK_DEC_THRESHOLD_USEC, &u->source->sample_spec);
 
         fix_min_sleep_wakeup(u);
         fix_tsched_watermark(u);
diff --git a/src/pulsecore/rtpoll.c b/src/pulsecore/rtpoll.c
index 42708a8a..666cbc98 100644
--- a/src/pulsecore/rtpoll.c
+++ b/src/pulsecore/rtpoll.c
@@ -63,6 +63,7 @@ struct pa_rtpoll {
     pa_bool_t running:1;
     pa_bool_t rebuild_needed:1;
     pa_bool_t quit:1;
+    pa_bool_t timer_elapsed:1;
 
 #ifdef DEBUG_TIMING
     pa_usec_t timestamp;
@@ -94,26 +95,14 @@ PA_STATIC_FLIST_DECLARE(items, 0, pa_xfree);
 pa_rtpoll *pa_rtpoll_new(void) {
     pa_rtpoll *p;
 
-    p = pa_xnew(pa_rtpoll, 1);
+    p = pa_xnew0(pa_rtpoll, 1);
 
     p->n_pollfd_alloc = 32;
     p->pollfd = pa_xnew(struct pollfd, p->n_pollfd_alloc);
     p->pollfd2 = pa_xnew(struct pollfd, p->n_pollfd_alloc);
-    p->n_pollfd_used = 0;
-
-    pa_zero(p->next_elapse);
-    p->timer_enabled = FALSE;
-
-    p->running = FALSE;
-    p->scan_for_dead = FALSE;
-    p->rebuild_needed = FALSE;
-    p->quit = FALSE;
-
-    PA_LLIST_HEAD_INIT(pa_rtpoll_item, p->items);
 
 #ifdef DEBUG_TIMING
     p->timestamp = pa_rtclock_now();
-    p->slept = p->awake = 0;
 #endif
 
     return p;
@@ -229,6 +218,7 @@ int pa_rtpoll_run(pa_rtpoll *p, pa_bool_t wait_op) {
     pa_assert(!p->running);
 
     p->running = TRUE;
+    p->timer_elapsed = FALSE;
 
     /* First, let's do some work */
     for (i = p->items; i && i->priority < PA_RTPOLL_NEVER; i = i->next) {
@@ -286,7 +276,7 @@ int pa_rtpoll_run(pa_rtpoll *p, pa_bool_t wait_op) {
     if (p->rebuild_needed)
         rtpoll_rebuild(p);
 
-    memset(&timeout, 0, sizeof(timeout));
+    pa_zero(timeout);
 
     /* Calculate timeout */
     if (wait_op && !p->quit && p->timer_enabled) {
@@ -314,9 +304,11 @@ int pa_rtpoll_run(pa_rtpoll *p, pa_bool_t wait_op) {
         r = ppoll(p->pollfd, p->n_pollfd_used, (!wait_op || p->quit || p->timer_enabled) ? &ts : NULL, NULL);
     }
 #else
-        r = poll(p->pollfd, p->n_pollfd_used, (!wait_op || p->quit || p->timer_enabled) ? (int) ((timeout.tv_sec*1000) + (timeout.tv_usec / 1000)) : -1);
+    r = poll(p->pollfd, p->n_pollfd_used, (!wait_op || p->quit || p->timer_enabled) ? (int) ((timeout.tv_sec*1000) + (timeout.tv_usec / 1000)) : -1);
 #endif
 
+    p->timer_elapsed = r == 0;
+
 #ifdef DEBUG_TIMING
     {
         pa_usec_t now = pa_rtclock_now();
@@ -628,3 +620,9 @@ void pa_rtpoll_quit(pa_rtpoll *p) {
 
     p->quit = TRUE;
 }
+
+pa_bool_t pa_rtpoll_timer_elapsed(pa_rtpoll *p) {
+    pa_assert(p);
+
+    return p->timer_elapsed;
+}
diff --git a/src/pulsecore/rtpoll.h b/src/pulsecore/rtpoll.h
index d2d69cad..b2a87fca 100644
--- a/src/pulsecore/rtpoll.h
+++ b/src/pulsecore/rtpoll.h
@@ -73,6 +73,10 @@ void pa_rtpoll_set_timer_absolute(pa_rtpoll *p, pa_usec_t usec);
 void pa_rtpoll_set_timer_relative(pa_rtpoll *p, pa_usec_t usec);
 void pa_rtpoll_set_timer_disabled(pa_rtpoll *p);
 
+/* Return TRUE when the elapsed timer was the reason for
+ * the last pa_rtpoll_run() invocation to finish */
+pa_bool_t pa_rtpoll_timer_elapsed(pa_rtpoll *p);
+
 /* A new fd wakeup item for pa_rtpoll */
 pa_rtpoll_item *pa_rtpoll_item_new(pa_rtpoll *p, pa_rtpoll_priority_t prio, unsigned n_fds);
 void pa_rtpoll_item_free(pa_rtpoll_item *i);