Re: [FFmpeg-devel] [PATCH 01/14] vvcdec: add thread executor

["Rémi Denis-Courmont" <remi@remlab.net>]

Le sunnuntaina 21. toukokuuta 2023, 16.03.06 EEST Nuo Mi a écrit :
> The executor design pattern was inroduced by java
> <https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/util/conc
> urrent/Executor.html> it also adapted by python
> <https://docs.python.org/3/library/concurrent.futures.html>
> Compared to handcrafted thread pool management, it greatly simplifies the
> thread code. ---
>  libavcodec/Makefile           |   1 +
>  libavcodec/vvc/Makefile       |   4 +
>  libavcodec/vvc/vvc_executor.c | 193 ++++++++++++++++++++++++++++++++++
>  libavcodec/vvc/vvc_executor.h |  73 +++++++++++++
>  4 files changed, 271 insertions(+)
>  create mode 100644 libavcodec/vvc/Makefile
>  create mode 100644 libavcodec/vvc/vvc_executor.c
>  create mode 100644 libavcodec/vvc/vvc_executor.h
> 
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index dab09f483a..b1fcbf71b2 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -62,6 +62,7 @@ OBJS = ac3_parser.o                                       
>              \ xiph.o                                                      
>     \
> 
>  # subsystems
> +include $(SRC_PATH)/libavcodec/vvc/Makefile
>  OBJS-$(CONFIG_AANDCTTABLES)            += aandcttab.o
>  OBJS-$(CONFIG_AC3DSP)                  += ac3dsp.o ac3.o ac3tab.o
>  OBJS-$(CONFIG_ADTS_HEADER)             += adts_header.o
> mpeg4audio_sample_rates.o diff --git a/libavcodec/vvc/Makefile
> b/libavcodec/vvc/Makefile
> new file mode 100644
> index 0000000000..c4b93e0389
> --- /dev/null
> +++ b/libavcodec/vvc/Makefile
> @@ -0,0 +1,4 @@
> +clean::
> +	$(RM) $(CLEANSUFFIXES:%=libavcodec/vvc/%)
> +
> +OBJS-$(CONFIG_VVC_DECODER)          +=  vvc/vvc_executor.o
> diff --git a/libavcodec/vvc/vvc_executor.c b/libavcodec/vvc/vvc_executor.c
> new file mode 100644
> index 0000000000..f2afdf79ae
> --- /dev/null
> +++ b/libavcodec/vvc/vvc_executor.c
> @@ -0,0 +1,193 @@
> +/*
> + * VVC video Decoder
> + *
> + * Copyright (C) 2022 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 "libavutil/avutil.h"
> +#include "libavutil/thread.h"
> +
> +#include "vvc_executor.h"

This does not seem specific to VVC in any way, so the naming (and choice of 
folder placement) is rather weird.

> +
> +typedef struct ThreadInfo {
> +    int idx;
> +    VVCExecutor *e;
> +    pthread_t thread;
> +} ThreadInfo;
> +
> +struct VVCExecutor {
> +    VVCTaskCallbacks cb;
> +    ThreadInfo *threads;
> +    uint8_t *local_contexts;

It seems odd and needless complex to separate this from the thread info. It 
looks like you could simply append a pointer or a flexible array to ThreadInfo 
instead.

> +    int thread_count;
> +
> +    pthread_mutex_t lock;
> +    pthread_cond_t cond;
> +    int die;
> +    VVCTasklet *tasks;
> +};
> +
> +static void remove_task(VVCTasklet **prev, VVCTasklet *t)
> +{
> +    *prev  = t->next;
> +    t->next = NULL;
> +}
> +
> +static void add_task(VVCTasklet **prev, VVCTasklet *t)
> +{
> +    t->next = *prev;
> +    *prev   = t;
> +}
> +
> +static void *executor_worker_task(void *data)
> +{
> +    ThreadInfo *ti = (ThreadInfo*)data;
> +    VVCExecutor *e = ti->e;
> +    void *lc       = e->local_contexts + ti->idx *
> e->cb.local_context_size;
> +    VVCTasklet **prev;
> +    VVCTaskCallbacks *cb = &e->cb;
> +
> +    pthread_mutex_lock(&e->lock);
> +    while (1) {
> +        VVCTasklet* t = NULL;
> +        if (e->die) break;
> +
> +        for (prev = &e->tasks; *prev; prev = &(*prev)->next) {
> +            if (cb->ready(*prev, cb->user_data)) {
> +                t = *prev;
> +                break;
> +            }
> +        }
> +        if (t) {
> +            //found one task
> +            remove_task(prev, t);
> +            pthread_mutex_unlock(&e->lock);
> +            cb->run(t, lc, cb->user_data);
> +            pthread_mutex_lock(&e->lock);
> +        } else {
> +            //no task in one loop
> +            pthread_cond_wait(&e->cond, &e->lock);
> +        }
> +    }
> +    pthread_mutex_unlock(&e->lock);
> +    return NULL;
> +}
> +
> +VVCExecutor* ff_vvc_executor_alloc(const VVCTaskCallbacks *cb, int
> thread_count) +{
> +    VVCExecutor *e;
> +    int i, j, ret;
> +    if (!cb || !cb->user_data || !cb->ready || !cb->run ||
> !cb->priority_higher) +        return NULL;
> +    e = av_calloc(1, sizeof(*e));
> +    if (!e)
> +        return NULL;
> +    e->cb = *cb;
> +
> +    e->local_contexts = av_malloc(thread_count * e->cb.local_context_size);
> +    if (!e->local_contexts)
> +        goto free_executor;
> +
> +    e->threads = av_calloc(thread_count, sizeof(*e->threads));
> +    if (!e->threads)
> +        goto free_contexts;
> +    for (i = 0; i < thread_count; i++) {
> +        ThreadInfo *ti = e->threads + i;
> +        ti->e = e;
> +        ti->idx = i;
> +    }
> +
> +    ret = pthread_mutex_init(&e->lock, NULL);
> +    if (ret)
> +        goto free_threads;
> +
> +    ret = pthread_cond_init(&e->cond, NULL);
> +    if (ret)
> +        goto destroy_lock;
> +
> +    for (i = 0; i < thread_count; i++) {
> +        ThreadInfo *ti = e->threads + i;
> +        ret = pthread_create(&ti->thread, NULL, executor_worker_task, ti);
> +        if (ret)
> +            goto join_threads;
> +    }
> +    e->thread_count = thread_count;
> +    return e;
> +
> +join_threads:
> +    pthread_mutex_lock(&e->lock);
> +    e->die = 1;
> +    pthread_cond_broadcast(&e->cond);
> +    pthread_mutex_unlock(&e->lock);
> +    for (j = 0; j < i; j++)
> +        pthread_join(e->threads[j].thread, NULL);
> +    pthread_cond_destroy(&e->cond);
> +destroy_lock:
> +    pthread_mutex_destroy(&e->lock);
> +free_threads:
> +    av_free(e->threads);
> +free_contexts:
> +    av_free(e->local_contexts);
> +free_executor:
> +    free(e);
> +    return NULL;
> +}
> +
> +void ff_vvc_executor_free(VVCExecutor **executor)
> +{
> +    VVCExecutor *e;
> +    if (!executor || !*executor)
> +        return;
> +    e = *executor;
> +
> +    //singal die
> +    pthread_mutex_lock(&e->lock);
> +    e->die = 1;
> +    pthread_cond_broadcast(&e->cond);
> +    pthread_mutex_unlock(&e->lock);
> +
> +    for (int i = 0; i < e->thread_count; i++)
> +        pthread_join(e->threads[i].thread, NULL);
> +    pthread_cond_destroy(&e->cond);
> +    pthread_mutex_destroy(&e->lock);
> +
> +    av_free(e->threads);
> +    av_free(e->local_contexts);
> +
> +    av_freep(executor);
> +}
> +
> +void ff_vvc_executor_execute(VVCExecutor *e, VVCTasklet *t)
> +{
> +    VVCTaskCallbacks *cb = &e->cb;
> +    VVCTasklet **prev;
> +
> +    pthread_mutex_lock(&e->lock);
> +    for (prev = &e->tasks; *prev && cb->priority_higher(*prev, t); prev =
> &(*prev)->next) +        /* nothing */;
> +    add_task(prev, t);
> +    pthread_cond_signal(&e->cond);
> +    pthread_mutex_unlock(&e->lock);
> +}
> +
> +void ff_vvc_executor_wakeup(VVCExecutor *e)
> +{
> +    pthread_mutex_lock(&e->lock);
> +    pthread_cond_broadcast(&e->cond);
> +    pthread_mutex_unlock(&e->lock);

Signaling a condition variable without changing any state makes no sense.

> +}

-- 
Rémi Denis-Courmont
http://www.remlab.net/



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