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

[Thilo Borgmann]

Am 06.06.21 um 14:35 schrieb Andreas Rheinhardt:
> Thilo Borgmann:
>> Hi,
>>
>> add an option to override auto-detection of cpu count. Defaults to auto-detection, of course.
>>
>> -Thilo
>>
> 
>>
>>  doc/fftools-common-opts.texi |  7 +++++++
>>  fftools/cmdutils.c           | 27 +++++++++++++++++++++++++++
>>  fftools/cmdutils.h           |  7 +++++++
>>  libavutil/cpu.c              | 14 ++++++++++++++
>>  libavutil/cpu.h              |  6 ++++++
> 
> The changes to libavutil and cmdutils should be in separate patches; and
> of course the commit message should mention that you are changing
> libavutil -- I would have nearly missed this patch (given that I don't
> pay much attention to fftools in general).
> 
>>
>> diff --git a/libavutil/cpu.c b/libavutil/cpu.c
>> index 52f6b9a3bf..ccd5b5adac 100644
>> --- a/libavutil/cpu.c
>> +++ b/libavutil/cpu.c
> 
> 52f6b9a3bf is the state of cpu.c after
> e387fcd01cb84d9493f3b96158addd2a85f086c6. This is completely outdated.

Yes, messed up branches for the patch, thx!


>>
>> @@ -306,14 +307,27 @@ int av_cpu_count(void)
>>      nb_cpus = sysinfo.dwNumberOfProcessors;
>>  #endif
>>  
>> +    int count = atomic_load_explicit(&cpu_count, memory_order_relaxed);
>> +
>>      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;
>>  }
>>  
> In particular, this hunk doesn't apply to git master at all any more
> (did I already mention that cpu.c only has 245 lines atm, not >300?).
> And the declaration of count would lead to a statement-after-declaration
> warning.

Done locally to apply to today's HEAD. I think I'll wait with sending both patches once we decided on atomic loads in "[PATCH] Stop using _explicit atomic operations where not necessary.".

Thanks,
Thilo