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

[James Almer]

On 6/6/2021 7:44 AM, Thilo Borgmann wrote:
> 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.

Looks like you did not rename it to av_cpu_ namespace.

> 
> Thanks,
> Thilo
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