[FFmpeg-devel] [PATCH v3 1/3] avcodec: make a local copy of executor

James Almer jamrial at gmail.com
Tue Oct 1 17:03:54 EEST 2024


On 10/1/2024 10:54 AM, Nuo Mi wrote:
> We still need several refactors to improve the current VVC decoder's performance,
> which will frequently break the API/ABI. To mitigate this, we've copied the executor from
> avutil to avcodec. Once the API/ABI is stable, we will move this class back to avutil
> ---
>   libavcodec/Makefile     |   1 +
>   libavcodec/executor.c   | 221 ++++++++++++++++++++++++++++++++++++++++
>   libavcodec/executor.h   |  73 +++++++++++++
>   libavcodec/vvc/thread.c |   8 +-
>   4 files changed, 299 insertions(+), 4 deletions(-)
>   create mode 100644 libavcodec/executor.c
>   create mode 100644 libavcodec/executor.h
> 
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index a4fcce3b42..da1a1aa945 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -43,6 +43,7 @@ OBJS = ac3_parser.o                                                     \
>          dirac.o                                                          \
>          dv_profile.o                                                     \
>          encode.o                                                         \
> +       executor.o                                                       \
>          get_buffer.o                                                     \
>          imgconvert.o                                                     \
>          jni.o                                                            \
> diff --git a/libavcodec/executor.c b/libavcodec/executor.c
> new file mode 100644
> index 0000000000..f8fc7c33ab
> --- /dev/null
> +++ b/libavcodec/executor.c
> @@ -0,0 +1,221 @@
> +/*
> + * Copyright (C) 2024 Nuo Mi
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include "config.h"
> +
> +#include <stdbool.h>
> +
> +#include "libavutil/mem.h"
> +#include "libavutil/thread.h"
> +
> +#include "executor.h"
> +
> +#if !HAVE_THREADS
> +
> +#define ExecutorThread  char
> +
> +#define executor_thread_create(t, a, s, ar)      0
> +#define executor_thread_join(t, r)               do {} while(0)
> +
> +#else
> +
> +#define ExecutorThread  pthread_t
> +
> +#define executor_thread_create(t, a, s, ar)      pthread_create(t, a, s, ar)
> +#define executor_thread_join(t, r)               pthread_join(t, r)
> +
> +#endif //!HAVE_THREADS
> +
> +typedef struct ThreadInfo {
> +    AVExecutor *e;
> +    ExecutorThread thread;
> +} ThreadInfo;
> +
> +struct AVExecutor {
> +    AVTaskCallbacks cb;
> +    int thread_count;
> +    bool recursive;
> +
> +    ThreadInfo *threads;
> +    uint8_t *local_contexts;
> +
> +    AVMutex lock;
> +    AVCond cond;
> +    int die;
> +
> +    AVTask *tasks;
> +};
> +
> +static AVTask* remove_task(AVTask **prev, AVTask *t)
> +{
> +    *prev  = t->next;
> +    t->next = NULL;
> +    return t;
> +}
> +
> +static void add_task(AVTask **prev, AVTask *t)
> +{
> +    t->next = *prev;
> +    *prev   = t;
> +}
> +
> +static int run_one_task(AVExecutor *e, void *lc)
> +{
> +    AVTaskCallbacks *cb = &e->cb;
> +    AVTask **prev;
> +
> +    for (prev = &e->tasks; *prev && !cb->ready(*prev, cb->user_data); prev = &(*prev)->next)
> +        /* nothing */;
> +    if (*prev) {
> +        AVTask *t = remove_task(prev, *prev);
> +        if (e->thread_count > 0)
> +            ff_mutex_unlock(&e->lock);
> +        cb->run(t, lc, cb->user_data);
> +        if (e->thread_count > 0)
> +            ff_mutex_lock(&e->lock);
> +        return 1;
> +    }
> +    return 0;
> +}
> +
> +#if HAVE_THREADS
> +static void *executor_worker_task(void *data)
> +{
> +    ThreadInfo *ti = (ThreadInfo*)data;
> +    AVExecutor *e  = ti->e;
> +    void *lc       = e->local_contexts + (ti - e->threads) * e->cb.local_context_size;
> +
> +    ff_mutex_lock(&e->lock);
> +    while (1) {
> +        if (e->die) break;
> +
> +        if (!run_one_task(e, lc)) {
> +            //no task in one loop
> +            ff_cond_wait(&e->cond, &e->lock);
> +        }
> +    }
> +    ff_mutex_unlock(&e->lock);
> +    return NULL;
> +}
> +#endif
> +
> +static void executor_free(AVExecutor *e, const int has_lock, const int has_cond)
> +{
> +    if (e->thread_count) {
> +        //signal die
> +        ff_mutex_lock(&e->lock);
> +        e->die = 1;
> +        ff_cond_broadcast(&e->cond);
> +        ff_mutex_unlock(&e->lock);
> +
> +        for (int i = 0; i < e->thread_count; i++)
> +            executor_thread_join(e->threads[i].thread, NULL);
> +    }
> +    if (has_cond)
> +        ff_cond_destroy(&e->cond);
> +    if (has_lock)
> +        ff_mutex_destroy(&e->lock);
> +
> +    av_free(e->threads);
> +    av_free(e->local_contexts);
> +
> +    av_free(e);
> +}
> +
> +AVExecutor* ff_executor_alloc(const AVTaskCallbacks *cb, int thread_count)
> +{
> +    AVExecutor *e;
> +    int has_lock = 0, has_cond = 0;
> +    if (!cb || !cb->user_data || !cb->ready || !cb->run || !cb->priority_higher)
> +        return NULL;
> +
> +    e = av_mallocz(sizeof(*e));
> +    if (!e)
> +        return NULL;
> +    e->cb = *cb;
> +
> +    e->local_contexts = av_calloc(FFMAX(thread_count, 1), e->cb.local_context_size);
> +    if (!e->local_contexts)
> +        goto free_executor;
> +
> +    e->threads = av_calloc(FFMAX(thread_count, 1), sizeof(*e->threads));
> +    if (!e->threads)
> +        goto free_executor;
> +
> +    if (!thread_count)
> +        return e;
> +
> +    has_lock = !ff_mutex_init(&e->lock, NULL);
> +    has_cond = !ff_cond_init(&e->cond, NULL);
> +
> +    if (!has_lock || !has_cond)
> +        goto free_executor;
> +
> +    for (/* nothing */; e->thread_count < thread_count; e->thread_count++) {
> +        ThreadInfo *ti = e->threads + e->thread_count;
> +        ti->e = e;
> +        if (executor_thread_create(&ti->thread, NULL, executor_worker_task, ti))
> +            goto free_executor;
> +    }
> +    return e;
> +
> +free_executor:
> +    executor_free(e, has_lock, has_cond);
> +    return NULL;
> +}
> +
> +void ff_executor_free(AVExecutor **executor)
> +{
> +    int thread_count;
> +
> +    if (!executor || !*executor)
> +        return;
> +    thread_count = (*executor)->thread_count;
> +    executor_free(*executor, thread_count, thread_count);
> +    *executor = NULL;
> +}
> +
> +void ff_executor_execute(AVExecutor *e, AVTask *t)
> +{
> +    AVTaskCallbacks *cb = &e->cb;
> +    AVTask **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 (e->thread_count) {
> +        ff_cond_signal(&e->cond);
> +        ff_mutex_unlock(&e->lock);
> +    }
> +
> +    if (!e->thread_count || !HAVE_THREADS) {
> +        if (e->recursive)
> +            return;
> +        e->recursive = true;
> +        // We are running in a single-threaded environment, so we must handle all tasks ourselves
> +        while (run_one_task(e, e->local_contexts))
> +            /* nothing */;
> +        e->recursive = false;
> +    }
> +}
> diff --git a/libavcodec/executor.h b/libavcodec/executor.h
> new file mode 100644
> index 0000000000..05d4b1e189
> --- /dev/null
> +++ b/libavcodec/executor.h
> @@ -0,0 +1,73 @@
> +/*
> + * Copyright (C) 2024 Nuo Mi
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +/*
> + * We still need several refactors to improve the current VVC decoder's performance,
> + * which will frequently break the API/ABI. To mitigate this, we've copied the executor from
> + * avutil to avcodec. Once the API/ABI is stable, we will move this class back to avutil
> + */
> +
> +#ifndef AVCODEC_EXECUTOR_H
> +#define AVCODEC_EXECUTOR_H
> +
> +typedef struct AVExecutor AVExecutor;
> +typedef struct AVTask AVTask;
> +
> +struct AVTask {
> +    AVTask *next;
> +};
> +
> +typedef struct AVTaskCallbacks {

Should probably use a different namespace for this header, to ensure it 
doesn't conflict with the lavu one. So just prefix everything with FF 
instead of AV.

> +    void *user_data;
> +
> +    int local_context_size;
> +
> +    // return 1 if a's priority > b's priority
> +    int (*priority_higher)(const AVTask *a, const AVTask *b);
> +
> +    // task is ready for run
> +    int (*ready)(const AVTask *t, void *user_data);
> +
> +    // run the task
> +    int (*run)(AVTask *t, void *local_context, void *user_data);
> +} AVTaskCallbacks;
> +
> +/**
> + * Alloc executor
> + * @param callbacks callback structure for executor
> + * @param thread_count worker thread number, 0 for run on caller's thread directly
> + * @return return the executor
> + */
> +AVExecutor* ff_executor_alloc(const AVTaskCallbacks *callbacks, int thread_count);
> +
> +/**
> + * Free executor
> + * @param e  pointer to executor
> + */
> +void ff_executor_free(AVExecutor **e);
> +
> +/**
> + * Add task to executor
> + * @param e pointer to executor
> + * @param t pointer to task. If NULL, it will wakeup one work thread
> + */
> +void ff_executor_execute(AVExecutor *e, AVTask *t);
> +
> +#endif //AVCODEC_EXECUTOR_H
> diff --git a/libavcodec/vvc/thread.c b/libavcodec/vvc/thread.c
> index 86a7753c6a..72f5c51382 100644
> --- a/libavcodec/vvc/thread.c
> +++ b/libavcodec/vvc/thread.c
> @@ -22,7 +22,7 @@
>   
>   #include <stdatomic.h>
>   
> -#include "libavutil/executor.h"
> +#include "libavcodec/executor.h"
>   #include "libavutil/mem.h"
>   #include "libavutil/thread.h"
>   
> @@ -109,7 +109,7 @@ static void add_task(VVCContext *s, VVCTask *t)
>   
>       atomic_fetch_add(&ft->nb_scheduled_tasks, 1);
>   
> -    av_executor_execute(s->executor, &t->u.task);
> +    ff_executor_execute(s->executor, &t->u.task);
>   }
>   
>   static void task_init(VVCTask *t, VVCTaskStage stage, VVCFrameContext *fc, const int rx, const int ry)
> @@ -692,12 +692,12 @@ AVExecutor* ff_vvc_executor_alloc(VVCContext *s, const int thread_count)
>           task_ready,
>           task_run,
>       };
> -    return av_executor_alloc(&callbacks, thread_count);
> +    return ff_executor_alloc(&callbacks, thread_count);
>   }
>   
>   void ff_vvc_executor_free(AVExecutor **e)
>   {
> -    av_executor_free(e);
> +    ff_executor_free(e);
>   }
>   
>   void ff_vvc_frame_thread_free(VVCFrameContext *fc)

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