[FFmpeg-devel] [PATCH] fftools/cmdutils.c: Add cmd line option to override detection of cpu count

[Thilo Borgmann]

Hi,

Am 05.06.21 um 16:33 schrieb Anton Khirnov:
> 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.borgmann at 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: ffmpeg at 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(+)
>>
>> [...]

>>  /**
>>   * 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().
> 
>> [...]

>> +/**
>> + * 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_

For both of these, I copied the behavior of av_force_cpu_flags(). For function names as well as the atomic load.
Let me know which way you prefer. If you prefer your reviewed version, I could also send a patch for similar changes to av_force_cpu_flags() if that makes sense.

All other remarks changed locally.

Thanks,
Thilo