On Fri, 17 Jan 2020 06:37:16 +0100, Keyon Jie wrote: > > On 2020/1/17 上午1:40, Pierre-Louis Bossart wrote: > > > >>>>> So, do you suggest not doing preallocation(or calling it with 0 > >>>>> size) for all > >>>>> driver with TYPE_SG? I am fine if this is the recommended > >>>>> method, I can try > >>>>> this on SOF I2S platform to see if it can work as we required > >>>>> for very large > >>>>> buffer size. > >>> > >>> Keyon, for the rest of us to follow this patch, would you mind > >>> clarifying what drives the need for a 'very large buffer size', > >>> and what order of magnitude this very large size would be. > >>> > >>> FWIW, we've measured consistently on different Windows/Linux > >>> platforms, maybe 10 years ago, that once you reach a buffer of 1s > >>> (384 kB) the benefits from increasing that buffer size further are > >>> marginal in terms of power consumption, and generate all kinds of > >>> issues with volume updates and deferred routing changes. > >>> > >> We need bigger buffer on host side to compensate the wake up time > >> from d0ix to d0 which takes ~2 seconds on my setup. So, wiith > >> smaller buffer sizes like < 2 seconds we overwrite data since FW > >> keeps copping while host doesn't read until its up and running > >> again. > > > > Right, that's a valid case, but that's 256 kB, not 'very large' or > > likely to ever trigger an OOM case. > > For S24_LE, it is 512KB, the point is that if we can't re-allocate > buffer at hw_params() stage, then we need follow a BKM that we have to > preallocate the largest DMA buffer that we claim to support at > pcm_new(), I think this is actually another kind of wast with these > largest pinned buffer that can't be swapped out... Well, that's the case you'd need a larger preallocation. I guess many distros already set it to a higher value for PulseAudio. The default 64kB is just from historical and compatibility reason, and we may extend it to 1MB or so now. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
