From: Keyon Jie <yang.jie@linux.intel.com> To: Takashi Iwai <tiwai@suse.de>, Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>, "Rajwa, Marcin" <marcin.rajwa@linux.intel.com> Subject: Re: [alsa-devel] [PATCH] ALSA: pcm: fix buffer_bytes max constrained by preallocated bytes issue Date: Fri, 17 Jan 2020 13:30:18 +0800 Message-ID: <a1b549b7-a902-b2ee-e2e4-53f73893def3@linux.intel.com> (raw) In-Reply-To: <s5h5zhbp27i.wl-tiwai@suse.de> On 2020/1/17 上午4:37, Takashi Iwai wrote: > On Thu, 16 Jan 2020 18:40:26 +0100, > 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. > > That size shouldn't matter, and would work even with the > preallocation. > > My concern is that removing the limitation would allow the allocation > of too large sizes. Even with dma_max limit, it can go up to 32MB > physical pages per stream for HDA. Depending on the hardware setup, > there can be a lot of streams assignment (e.g. HDMI codecs) and > multiple codecs / controllers, and imagine that all those allocated > pages are pinned and can't be swapped out... Hi Takashi, I get your concern here, but if we switch to use dma_max limit, we won't change the preallocated buffer, it will be still 64KB for each stream, user space can ask for re-allocate buffer for each stream up to 32MB, but those pinned and can't be swapped out ones are the 64KB preallocated ones only, am I wrong? Thanks, ~Keyon > > > Takashi > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@alsa-project.org > https://mailman.alsa-project.org/mailman/listinfo/alsa-devel > _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
next prev parent reply index Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-16 4:53 Keyon Jie 2020-01-16 7:15 ` Takashi Iwai 2020-01-16 9:50 ` Keyon Jie 2020-01-16 10:27 ` Takashi Iwai 2020-01-16 11:25 ` Keyon Jie 2020-01-16 11:50 ` Takashi Iwai 2020-01-16 14:14 ` Jie, Yang 2020-01-16 15:31 ` Jie, Yang 2020-01-16 16:07 ` Takashi Iwai 2020-01-16 16:39 ` Pierre-Louis Bossart 2020-01-16 17:25 ` Rajwa, Marcin 2020-01-16 17:40 ` Pierre-Louis Bossart 2020-01-16 20:37 ` Takashi Iwai 2020-01-17 5:30 ` Keyon Jie [this message] 2020-01-17 7:57 ` Takashi Iwai 2020-01-17 10:13 ` Keyon Jie 2020-01-17 10:30 ` Takashi Iwai 2020-01-17 10:56 ` Keyon Jie 2020-01-17 11:15 ` Takashi Iwai 2020-01-17 5:37 ` Keyon Jie 2020-01-17 8:00 ` Takashi Iwai 2020-01-17 10:43 ` Keyon Jie 2020-01-17 11:12 ` Takashi Iwai 2020-01-19 3:52 ` Keyon Jie 2020-01-19 7:09 ` Takashi Iwai 2020-01-19 8:11 ` Keyon Jie 2020-01-19 9:04 ` Takashi Iwai 2020-01-19 10:14 ` Keyon Jie 2020-01-19 10:43 ` Takashi Iwai 2020-01-20 2:23 ` Keyon Jie 2020-01-16 15:45 ` Takashi Iwai
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