On 2020/1/19 下午3:09, Takashi Iwai wrote:
On Sun, 19 Jan 2020 04:52:55 +0100, Keyon Jie wrote:
On 2020/1/17 下午7:12, Takashi Iwai wrote:
On Fri, 17 Jan 2020 11:43:24 +0100, Keyon Jie wrote:
In SOF driver, we don't use kernel config item like CONFIG_SND_HDA_PREALLOC_SIZE for HDA, the code for it is:
snd_pcm_lib_preallocate_pages(pcm->streams[stream].substream, SNDRV_DMA_TYPE_DEV_SG, sdev->dev, le32_to_cpu(caps->buffer_size_min), le32_to_cpu(caps->buffer_size_max));
So the preallocated size is configured via topology file, that is caps->buffer_size_min, no chance for PulseAudio to reconfigure it.
So, it looks like we have to change it to this if we don't change the ALSA core:
snd_pcm_lib_preallocate_pages(pcm->streams[stream].substream, SNDRV_DMA_TYPE_DEV_SG, sdev->dev,
le32_to_cpu(caps->buffer_size_min),
le32_to_cpu(caps->buffer_size_max), le32_to_cpu(caps->buffer_size_max));Yes, passing buffer_size_min for the preallocation sounds already bad. The default value should be sufficient for usual operations, not the cost-cutting minimum. Otherwise there is no merit of preallocation.
Alternatively, we may pass 0 there, indicating no limitation, too. But, this would need a bit other adjustment, e.g. snd_pcm_hardware should have lower buffer_bytes_max.
Thank you Takashi, then let's follow it to pre-allocate with caps->buffer_size_max, as we don't specify any limitations in snd_pcm_hardware today, we want to leave it configurable to each specific topology file for different machines.
How big is caps->buffer_size_max? Passing the value there means actually trying to allocate the given size as default, and it'd be a lot of waste if a too large value (e.g. 32MB) is passed there.
It varies for each stream, most of them are 65536 Bytes only, whereas one for Wake-On-Voice might need a > 4 Seconds buffer could be up to about 1~2MBytes, and another one for deep-buffer playback can be up to about 8MBytes.
I think we can go for passing zero as default, which means skipping preallocation. In addition, we may add an upper limit of the total
Just did an experiment and this works for me, I believe we still need to call snd_pcm_set_managed_buffer() though the preallocation is skipped in this, right?
amount of allocation per card, controlled in pcm_memory.c, for example. This logic can be applied to the legacy HDA, too.
This should be relatively easy, and I'll provide the patch in the next week.
OK, that's fine for me also, thank you.
~Keyon
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