avcodec/vvc: simplify priority logical to improve performance for 4K/8K

For 4K/8K video processing, it's possible to have over 1,000 tasks pending on the executor.
In such cases, O(n) and O(log(n)) insertion times are too costly.
Reducing this to O(1) will significantly decrease the time spent in critical sections

clip                                                        | before | after  | delta
------------------------------------------------------------|--------|--------|-------
VVC_HDR_UHDTV2_OpenGOP_7680x4320_50fps_HLG10.bit            |    24  |   27   |  12.5%
VVC_HDR_UHDTV2_OpenGOP_7680x4320_50fps_HLG10_HighBitrate.bit|    12  |   17   |  41.7%
tears_of_steel_4k_8M_8bit_2000.vvc                          |    34  |  102   | 200.0%
VVC_UHDTV1_OpenGOP_3840x2160_60fps_HLG10.bit                |   126  |  128   |   1.6%
RitualDance_1920x1080_60_10_420_37_RA.266                   |   350  |  378   |   8.0%
NovosobornayaSquare_1920x1080.bin                           |   341  |  369   |   8.2%
Tango2_3840x2160_60_10_420_27_LD.266                        |    69  |   70   |   1.4%
RitualDance_1920x1080_60_10_420_32_LD.266                   |   243  |  259   |   6.6%
Chimera_8bit_1080P_1000_frames.vvc                          |   420  |  392   |  -6.7%
BQTerrace_1920x1080_60_10_420_22_RA.vvc                     |   148  |  144   |  -2.7%

3 files changed, 55 insertions, 50 deletions

diff --git a/libavcodec/executor.c b/libavcodec/executor.c
index 21ebad3def..7a86e894f8 100644
--- a/libavcodec/executor.c
+++ b/libavcodec/executor.c
@@ -48,6 +48,11 @@ typedef struct ThreadInfo {
     ExecutorThread thread;
 } ThreadInfo;
 
+typedef struct Queue {
+    FFTask *head;
+    FFTask *tail;
+} Queue;
+
 struct FFExecutor {
     FFTaskCallbacks cb;
     int thread_count;
@@ -60,29 +65,39 @@ struct FFExecutor {
     AVCond cond;
     int die;
 
-    FFTask *tasks;
+    Queue *q;
 };
 
-static FFTask* remove_task(FFTask **prev, FFTask *t)
+static FFTask* remove_task(Queue *q)
 {
-    *prev  = t->next;
-    t->next = NULL;
+    FFTask *t = q->head;
+    if (t) {
+        q->head = t->next;
+        t->next = NULL;
+        if (!q->head)
+            q->tail = NULL;
+    }
     return t;
 }
 
-static void add_task(FFTask **prev, FFTask *t)
+static void add_task(Queue *q, FFTask *t)
 {
-    t->next = *prev;
-    *prev   = t;
+    t->next = NULL;
+    if (!q->head)
+        q->tail = q->head = t;
+    else
+        q->tail = q->tail->next = t;
 }
 
 static int run_one_task(FFExecutor *e, void *lc)
 {
     FFTaskCallbacks *cb = &e->cb;
-    FFTask **prev = &e->tasks;
+    FFTask *t = NULL;
+
+    for (int i = 0; i < e->cb.priorities && !t; i++)
+        t = remove_task(e->q + i);
 
-    if (*prev) {
-        FFTask *t = remove_task(prev, *prev);
+    if (t) {
         if (e->thread_count > 0)
             ff_mutex_unlock(&e->lock);
         cb->run(t, lc, cb->user_data);
@@ -132,6 +147,7 @@ static void executor_free(FFExecutor *e, const int has_lock, const int has_cond)
         ff_mutex_destroy(&e->lock);
 
     av_free(e->threads);
+    av_free(e->q);
     av_free(e->local_contexts);
 
     av_free(e);
@@ -141,7 +157,7 @@ FFExecutor* ff_executor_alloc(const FFTaskCallbacks *cb, int thread_count)
 {
     FFExecutor *e;
     int has_lock = 0, has_cond = 0;
-    if (!cb || !cb->user_data || !cb->run || !cb->priority_higher)
+    if (!cb || !cb->user_data || !cb->run || !cb->priorities)
         return NULL;
 
     e = av_mallocz(sizeof(*e));
@@ -153,6 +169,10 @@ FFExecutor* ff_executor_alloc(const FFTaskCallbacks *cb, int thread_count)
     if (!e->local_contexts)
         goto free_executor;
 
+    e->q = av_calloc(e->cb.priorities, sizeof(Queue));
+    if (!e->q)
+        goto free_executor;
+
     e->threads = av_calloc(FFMAX(thread_count, 1), sizeof(*e->threads));
     if (!e->threads)
         goto free_executor;
@@ -192,16 +212,10 @@ void ff_executor_free(FFExecutor **executor)
 
 void ff_executor_execute(FFExecutor *e, FFTask *t)
 {
-    FFTaskCallbacks *cb = &e->cb;
-    FFTask **prev;
-
     if (e->thread_count)
         ff_mutex_lock(&e->lock);
-    if (t) {
-        for (prev = &e->tasks; *prev && cb->priority_higher(*prev, t); prev = &(*prev)->next)
-            /* nothing */;
-        add_task(prev, t);
-    }
+    if (t)
+        add_task(e->q + t->priority % e->cb.priorities, t);
     if (e->thread_count) {
         ff_cond_signal(&e->cond);
         ff_mutex_unlock(&e->lock);
diff --git a/libavcodec/executor.h b/libavcodec/executor.h
index 51763ec25e..cd13d4c518 100644
--- a/libavcodec/executor.h
+++ b/libavcodec/executor.h
@@ -32,6 +32,7 @@ typedef struct FFTask FFTask;
 
 struct FFTask {
     FFTask *next;
+    int priority;   // task priority should >= 0 and < AVTaskCallbacks.priorities
 };
 
 typedef struct FFTaskCallbacks {
@@ -39,8 +40,8 @@ typedef struct FFTaskCallbacks {
 
     int local_context_size;
 
-    // return 1 if a's priority > b's priority
-    int (*priority_higher)(const FFTask *a, const FFTask *b);
+    // how many priorities do we have？
+    int priorities;
 
     // run the task
     int (*run)(FFTask *t, void *local_context, void *user_data);
diff --git a/libavcodec/vvc/thread.c b/libavcodec/vvc/thread.c
index a8c19b17cf..d75784e242 100644
--- a/libavcodec/vvc/thread.c
+++ b/libavcodec/vvc/thread.c
@@ -103,13 +103,28 @@ typedef struct VVCFrameThread {
     AVCond  cond;
 } VVCFrameThread;
 
+#define PRIORITY_LOWEST 2
 static void add_task(VVCContext *s, VVCTask *t)
 {
-    VVCFrameThread *ft = t->fc->ft;
+    VVCFrameThread *ft     = t->fc->ft;
+    FFTask *task           = &t->u.task;
+    const int priorities[] = {
+        0,                  // VVC_TASK_STAGE_INIT,
+        0,                  // VVC_TASK_STAGE_PARSE,
+        // For an 8K clip, a CTU line completed in the reference frame may trigger 64 and more inter tasks.
+        // We assign these tasks the lowest priority to avoid being overwhelmed with inter tasks.
+        PRIORITY_LOWEST,    // VVC_TASK_STAGE_INTER
+        1,                  // VVC_TASK_STAGE_RECON,
+        1,                  // VVC_TASK_STAGE_LMCS,
+        1,                  // VVC_TASK_STAGE_DEBLOCK_V,
+        1,                  // VVC_TASK_STAGE_DEBLOCK_H,
+        1,                  // VVC_TASK_STAGE_SAO,
+        1,                  // VVC_TASK_STAGE_ALF,
+    };
 
     atomic_fetch_add(&ft->nb_scheduled_tasks, 1);
-
-    ff_executor_execute(s->executor, &t->u.task);
+    task->priority = priorities[t->stage];
+    ff_executor_execute(s->executor, task);
 }
 
 static void task_init(VVCTask *t, VVCTaskStage stage, VVCFrameContext *fc, const int rx, const int ry)
@@ -372,31 +387,6 @@ static int task_is_stage_ready(VVCTask *t, int add)
     return task_has_target_score(t, stage, score);
 }
 
-#define CHECK(a, b)                         \
-    do {                                    \
-        if ((a) != (b))                     \
-            return (a) < (b);               \
-    } while (0)
-
-static int task_priority_higher(const FFTask *_a, const FFTask *_b)
-{
-    const VVCTask *a = (const VVCTask*)_a;
-    const VVCTask *b = (const VVCTask*)_b;
-
-
-    if (a->stage <= VVC_TASK_STAGE_PARSE || b->stage <= VVC_TASK_STAGE_PARSE) {
-        CHECK(a->stage, b->stage);
-        CHECK(a->fc->decode_order, b->fc->decode_order);           //decode order
-        CHECK(a->ry, b->ry);
-        return a->rx < b->rx;
-    }
-
-    CHECK(a->fc->decode_order, b->fc->decode_order);              //decode order
-    CHECK(a->rx + a->ry + a->stage, b->rx + b->ry + b->stage);    //zigzag with type
-    CHECK(a->rx + a->ry, b->rx + b->ry);                          //zigzag
-    return a->ry < b->ry;
-}
-
 static void check_colocation(VVCContext *s, VVCTask *t)
 {
     const VVCFrameContext *fc = t->fc;
@@ -681,7 +671,7 @@ FFExecutor* ff_vvc_executor_alloc(VVCContext *s, const int thread_count)
     FFTaskCallbacks callbacks = {
         s,
         sizeof(VVCLocalContext),
-        task_priority_higher,
+        PRIORITY_LOWEST + 1,
         task_run,
     };
     return ff_executor_alloc(&callbacks, thread_count);