Quoting Thilo Borgmann (2021-06-05 14:29:05)
> Hi,
>
> add an option to override auto-detection of cpu count. Defaults to
> auto-detection, of course.
>
> -Thilo
>
> From 38612f3e1339354dbaa6be4f36072320ff71c707 Mon Sep 17 00:00:00 2001
> From: Thilo Borgmann <thilo.borgm...@mail.de>
> Date: Sat, 5 Jun 2021 14:26:23 +0200
> Subject: [PATCH] fftools/cmdutils.c: Add cmd line option to override detection
> of cpu count
>
> Suggested-By: ffm...@fb.com
> ---
> doc/fftools-common-opts.texi | 7 +++++++
> fftools/cmdutils.c | 27 +++++++++++++++++++++++++++
> fftools/cmdutils.h | 7 +++++++
> libavutil/cpu.c | 14 ++++++++++++++
> libavutil/cpu.h | 6 ++++++
> 5 files changed, 61 insertions(+)
>
> diff --git a/doc/fftools-common-opts.texi b/doc/fftools-common-opts.texi
> index 5260ecb8f3..7643dd8396 100644
> --- a/doc/fftools-common-opts.texi
> +++ b/doc/fftools-common-opts.texi
> @@ -353,6 +353,13 @@ Possible flags for this option are:
> @end table
> @end table
>
> +@item -cpucount @var{count} (@emph{global})
> +Override detection of CPU count. This option is intended
> +for testing. Do not use it unless you know what you're doing.
> +@example
> +ffmpeg -cpucount 2
> +@end example
> +
> @item -max_alloc @var{bytes}
> Set the maximum size limit for allocating a block on the heap by ffmpeg's
> family of malloc functions. Exercise @strong{extreme caution} when using
> diff --git a/fftools/cmdutils.c b/fftools/cmdutils.c
> index 4eb68d2201..583a706e5d 100644
> --- a/fftools/cmdutils.c
> +++ b/fftools/cmdutils.c
> @@ -72,6 +72,7 @@ AVDictionary *format_opts, *codec_opts, *resample_opts;
> static FILE *report_file;
> static int report_file_level = AV_LOG_DEBUG;
> int hide_banner = 0;
> +int cpu_count = -1;
>
> enum show_muxdemuxers {
> SHOW_DEFAULT,
> @@ -866,6 +867,32 @@ int opt_cpuflags(void *optctx, const char *opt, const
> char *arg)
> return 0;
> }
>
> +int opt_cpucount(void *optctx, const char *opt, const char *arg)
> +{
> + int ret;
> + int count;
> +
> + static const AVOption opts[] = {
> + {"count", NULL, 0, AV_OPT_TYPE_INT, { .i64 = -1}, -1, INT_MAX, NULL},
> + {NULL},
> + };
> + static const AVClass class = {
> + .class_name = "cpucount",
> + .item_name = av_default_item_name,
> + .option = opts,
> + .version = LIBAVUTIL_VERSION_INT,
> + };
> + const AVClass *pclass = &class;
> +
> + ret = av_opt_eval_int(&pclass, opts, arg, &count);
> +
> + if (!ret) {
> + av_force_cpu_count(count);
> + }
> +
> + return ret;
This looks way overcomplicated. Why not just call strtol on arg?
> +}
> +
> int opt_loglevel(void *optctx, const char *opt, const char *arg)
> {
> const struct { const char *name; int level; } log_levels[] = {
> diff --git a/fftools/cmdutils.h b/fftools/cmdutils.h
> index 1917510589..29a45dd0be 100644
> --- a/fftools/cmdutils.h
> +++ b/fftools/cmdutils.h
> @@ -50,6 +50,7 @@ extern AVDictionary *sws_dict;
> extern AVDictionary *swr_opts;
> extern AVDictionary *format_opts, *codec_opts, *resample_opts;
> extern int hide_banner;
> +extern int cpu_count;
>
> /**
> * Register a program-specific cleanup routine.
> @@ -88,6 +89,11 @@ void log_callback_help(void* ptr, int level, const char*
> fmt, va_list vl);
> */
> int opt_cpuflags(void *optctx, const char *opt, const char *arg);
>
> +/**
> + * Override the cpucount.
> + */
> +int opt_cpucount(void *optctx, const char *opt, const char *arg);
> +
> /**
> * Fallback for options that are not explicitly handled, these will be
> * parsed through AVOptions.
> @@ -239,6 +245,7 @@ void show_help_options(const OptionDef *options, const
> char *msg, int req_flags,
> { "report", 0, { .func_arg = opt_report },
> "generate a report" }, \
> { "max_alloc", HAS_ARG, { .func_arg = opt_max_alloc },
> "set maximum size of a single allocated block", "bytes" }, \
> { "cpuflags", HAS_ARG | OPT_EXPERT, { .func_arg = opt_cpuflags },
> "force specific cpu flags", "flags" }, \
> + { "cpucount", HAS_ARG | OPT_EXPERT, { .func_arg = opt_cpucount },
> "force specific cpu count", "count" }, \
> { "hide_banner", OPT_BOOL | OPT_EXPERT, {&hide_banner}, "do not show
> program banner", "hide_banner" }, \
> CMDUTILS_COMMON_OPTIONS_AVDEVICE
> \
>
> diff --git a/libavutil/cpu.c b/libavutil/cpu.c
> index 52f6b9a3bf..ccd5b5adac 100644
> --- a/libavutil/cpu.c
> +++ b/libavutil/cpu.c
> @@ -48,6 +48,7 @@
> #endif
>
> static atomic_int cpu_flags = ATOMIC_VAR_INIT(-1);
> +static atomic_int cpu_count = ATOMIC_VAR_INIT(-1);
>
> static int get_cpu_flags(void)
> {
> @@ -306,14 +307,27 @@ int av_cpu_count(void)
> nb_cpus = sysinfo.dwNumberOfProcessors;
> #endif
>
> + int count = atomic_load_explicit(&cpu_count, memory_order_relaxed);
Just use a normal atomic_load().
> +
> if (!printed) {
> av_log(NULL, AV_LOG_DEBUG, "detected %d logical cores\n", nb_cpus);
> + if (count > 0) {
> + av_log(NULL, AV_LOG_DEBUG, "overriding to %d logical cores\n",
> count);
> + }
> printed = 1;
> }
>
> + if (count > 0) {
> + nb_cpus = count;
> + }
> +
> return nb_cpus;
> }
>
> +void av_force_cpu_count(int count){
Style.
> + atomic_store_explicit(&cpu_count, count, memory_order_relaxed);
> +}
> +
> size_t av_cpu_max_align(void)
> {
> if (ARCH_MIPS)
> diff --git a/libavutil/cpu.h b/libavutil/cpu.h
> index 83099dd969..9c682ad50b 100644
> --- a/libavutil/cpu.h
> +++ b/libavutil/cpu.h
> @@ -119,6 +119,12 @@ int av_parse_cpu_caps(unsigned *flags, const char *s);
> */
> int av_cpu_count(void);
>
> +/**
> + * Overrides cpu count detection and forces the specified count.
> + * Count < 1 disables forcing of specific count.
> + */
> +void av_force_cpu_count(int count);
I'd prefer if the name was namespaced as av_cpu_
--
Anton Khirnov
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