Re: [PATCH] ASoC: SOF: Use high-priority workqueue for PCM period elapsed

On 31/07/2026 12:20, Pierre-Louis Bossart wrote:
> On 7/30/26 15:04, Peter Ujfalusi wrote:
>> From: Yu-Hsuan Hsu <[email protected]>
>>
>> The snd_sof_pcm_period_elapsed function currently schedules work on the
>> system-wide workqueue. This can lead to potential delays or jitter in
>> audio processing if the system workqueue is busy with other tasks.
>>
>> To improve real-time performance and ensure timely processing of PCM
>> periods, we can use the system_highpri_wq instead of the default work
>> queue.
>>
>> In performance testing, this change significantly reduced the observed
>> scheduling delays. For instance, under load(stressapptest -M 15000 -m
>> 60), the maximum delay dropped from 9ms on the system workqueue to 5ms
>> on the dedicated high-priority workqueue.
>>
>> Suggested-by: Kai Vehmanen <[email protected]>
>> Signed-off-by: Yu-Hsuan Hsu <[email protected]>
>> Reviewed-by: Péter Ujfalusi <[email protected]>
>> Reviewed-by: Kai Vehmanen <[email protected]>
>> Reviewed-by: Bard Liao <[email protected]>
>> Signed-off-by: Peter Ujfalusi <[email protected]>
> 
> Sounds good but should this higher priority queue be used for other
> things as well?
> 
> e.g.
> 
> period-elapsed for compressed streams:
> schedule_work(&spcm->stream[cstream->direction].period_elapsed_work);
> 
> and the SoundWire interrupt handling with additional workqueues:
> schedule_work(&amd_manager->amd_sdw_irq_thread);
> schedule_work(&amd_manager->amd_sdw_work);
> schedule_work(&cdns->work);

we also have:
sound/soc/sof/core.c:           schedule_work(&sdev->probe_work);
sound/soc/sof/intel/ptl.c:      schedule_work(&hdev->mic_privacy.work);

> Not sure what the rules are to define what's high-priority and what's
> not... It could be that different systems have different requirements...

I think the 'rule' is that what is time critical and what can tolerate a
bit of a delay. The PCM period is time critical while the others are not
that much, that includes the compress elapsed, it is not that real-time
as the PCM.

But fair point, I will check if anything else would needs to be higher
priority than what they are.

> 
>> ---
>>  sound/soc/sof/pcm.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/sound/soc/sof/pcm.c b/sound/soc/sof/pcm.c
>> index b2071edeaea6..f748d072109a 100644
>> --- a/sound/soc/sof/pcm.c
>> +++ b/sound/soc/sof/pcm.c
>> @@ -62,7 +62,7 @@ void snd_sof_pcm_period_elapsed(struct snd_pcm_substream *substream)
>>  	 * To avoid sending IPC before the previous IPC is handled, we
>>  	 * schedule delayed work here to call the snd_pcm_period_elapsed().
>>  	 */
>> -	schedule_work(&spcm->stream[substream->stream].period_elapsed_work);
>> +	queue_work(system_highpri_wq, &spcm->stream[substream->stream].period_elapsed_work);
>>  }
>>  EXPORT_SYMBOL(snd_sof_pcm_period_elapsed);
>>  
> 

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