Re: [FFmpeg-devel] [PATCH 2/7] sws: add jobs option, distinct from threads

From: James Almer <jamrial@gmail.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 2/7] sws: add jobs option, distinct from threads
Date: Wed, 21 Sep 2022 15:25:02 -0300
Message-ID: <18093382-08c9-d44f-0d0d-683e82bd27fb@gmail.com> (raw)
In-Reply-To: <20220920175021.60790-3-rcombs@rcombs.me>

On 9/20/2022 2:50 PM, rcombs wrote:
> This allows for more efficient use of asymmetric-multiprocessing systems.
> ---
>   libswscale/options.c          | 2 ++
>   libswscale/swscale_internal.h | 1 +
>   libswscale/utils.c            | 9 ++++++---
>   libswscale/version.h          | 2 +-
>   4 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/libswscale/options.c b/libswscale/options.c
> index 4d41b835b1..5765daa100 100644
> --- a/libswscale/options.c
> +++ b/libswscale/options.c
> @@ -81,6 +81,8 @@ static const AVOption swscale_options[] = {
>   
>       { "threads",         "number of threads",             OFFSET(nb_threads),   AV_OPT_TYPE_INT, {.i64 = 1 }, 0, INT_MAX, VE, "threads" },
>           { "auto",        NULL,                            0,                  AV_OPT_TYPE_CONST, {.i64 = 0 },    .flags = VE, "threads" },
> +    { "jobs",            "number of jobs",                OFFSET(nb_jobs),      AV_OPT_TYPE_INT, {.i64 = 0 }, 0, INT_MAX, VE, "jobs" },

Default should probably be 1.

> +        { "auto",        NULL,                            0,                  AV_OPT_TYPE_CONST, {.i64 = 0 },    .flags = VE, "jobs" },
>   
>       { NULL }
>   };
> diff --git a/libswscale/swscale_internal.h b/libswscale/swscale_internal.h
> index abeebbb002..602082e12c 100644
> --- a/libswscale/swscale_internal.h
> +++ b/libswscale/swscale_internal.h
> @@ -339,6 +339,7 @@ typedef struct SwsContext {
>       int vChrDrop;                 ///< Binary logarithm of extra vertical subsampling factor in source image chroma planes specified by user.
>       int sliceDir;                 ///< Direction that slices are fed to the scaler (1 = top-to-bottom, -1 = bottom-to-top).
>       int nb_threads;               ///< Number of threads used for scaling
> +    int nb_jobs;                  ///< Number of slice jobs used for scaling
>       double param[2];              ///< Input parameters for scaling algorithms that need them.
>   
>       AVFrame *frame_src;
> diff --git a/libswscale/utils.c b/libswscale/utils.c
> index 45baa22b23..c9ff9db957 100644
> --- a/libswscale/utils.c
> +++ b/libswscale/utils.c
> @@ -1277,18 +1277,21 @@ static int context_init_threaded(SwsContext *c,
>                                       ff_sws_slice_worker, NULL, c->nb_threads);
>       if (ret == AVERROR(ENOSYS)) {
>           c->nb_threads = 1;
> +        c->nb_jobs = 1;
>           return 0;
>       } else if (ret < 0)
>           return ret;
>   
>       c->nb_threads = ret;
> +    if (c->nb_jobs < 1)

Can c->nb_jobs even be -1? The AVOption range above is 0..INT_MAX

> +        c->nb_jobs = av_cpu_job_count();
>   
> -    c->slice_ctx = av_calloc(c->nb_threads, sizeof(*c->slice_ctx));
> -    c->slice_err = av_calloc(c->nb_threads, sizeof(*c->slice_err));
> +    c->slice_ctx = av_calloc(c->nb_jobs, sizeof(*c->slice_ctx));
> +    c->slice_err = av_calloc(c->nb_jobs, sizeof(*c->slice_err));
>       if (!c->slice_ctx || !c->slice_err)
>           return AVERROR(ENOMEM);
>   
> -    for (int i = 0; i < c->nb_threads; i++) {
> +    for (int i = 0; i < c->nb_jobs; i++) {
>           c->slice_ctx[i] = sws_alloc_context();
>           if (!c->slice_ctx[i])
>               return AVERROR(ENOMEM);
> diff --git a/libswscale/version.h b/libswscale/version.h
> index 9bb3b171a7..4529a2d7d4 100644
> --- a/libswscale/version.h
> +++ b/libswscale/version.h
> @@ -29,7 +29,7 @@
>   #include "version_major.h"
>   
>   #define LIBSWSCALE_VERSION_MINOR   8
> -#define LIBSWSCALE_VERSION_MICRO 112
> +#define LIBSWSCALE_VERSION_MICRO 113
>   
>   #define LIBSWSCALE_VERSION_INT  AV_VERSION_INT(LIBSWSCALE_VERSION_MAJOR, \
>                                                  LIBSWSCALE_VERSION_MINOR, \
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