From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EE948C33CB1 for ; Thu, 16 Jan 2020 11:51:41 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7BC6820663 for ; Thu, 16 Jan 2020 11:51:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="pG45ry30" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7BC6820663 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id C9AC917A3; Thu, 16 Jan 2020 12:50:49 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz C9AC917A3 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1579175499; bh=HatlDVikLNq1m3E7HbICu1joKXJ7SHheyWaIdvXzBrM=; h=Date:From:To:In-Reply-To:References:Cc:Subject:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=pG45ry30qiX58CcGFioDwFKTHRr7QCncqjt4So8jW2sGnmcqAbQf/N2JKcNg1k++k 0GpQqrF3gyUdSXeviSCl7PEl3vral+xWpi/qLzuuxXa7i9/AKpBwTIIoe1sLAWfWou D4IpomAreYVlzcqykHsl8HruS++mrnJ85JmsR78w= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id 44C2AF8014D; Thu, 16 Jan 2020 12:50:49 +0100 (CET) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 0412CF8014E; Thu, 16 Jan 2020 12:50:46 +0100 (CET) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id DEFBAF80086 for ; Thu, 16 Jan 2020 12:50:39 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz DEFBAF80086 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id AEA65AFCD; Thu, 16 Jan 2020 11:50:38 +0000 (UTC) Date: Thu, 16 Jan 2020 12:50:37 +0100 Message-ID: From: Takashi Iwai To: Keyon Jie In-Reply-To: <3c0a0067043d614cd4491b28acf6d49640746b15.camel@linux.intel.com> References: <20200116045318.5498-1-yang.jie@linux.intel.com> <97bbe88d1a6b63fe8e9b02bf0c5ce4a80553c48d.camel@linux.intel.com> <3c0a0067043d614cd4491b28acf6d49640746b15.camel@linux.intel.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Cc: alsa-devel@alsa-project.org Subject: Re: [alsa-devel] [PATCH] ALSA: pcm: fix buffer_bytes max constrained by preallocated bytes issue X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Thu, 16 Jan 2020 12:25:38 +0100, Keyon Jie wrote: > > On Thu, 2020-01-16 at 11:27 +0100, Takashi Iwai wrote: > > On Thu, 16 Jan 2020 10:50:33 +0100, > > > > Oh, you're right, and I completely misread the patch. > > > > Now I took a coffee and can tell you the story behind the scene. > > > > I believe the current code is intentionally limiting the size to the > > preallocated size. This limitation was brought for not trying to > > allocate a larger buffer when the buffer has been preallocated. In > > the past, most hardware allocated the continuous pages for a buffer > > and the allocation of a large buffer fails quite likely. This was > > the > > reason of the buffer preallocation. So, the driver wanted to tell > > the > > user-space the limit. If user needs to have an extra large buffer, > > they are supposed to fiddle with prealloc procfs (either setting zero > > to clear the preallocation or setting a large enough buffer > > beforehand). > > Thank you for the sharing, it is interesting and knowledge learned to > me. > > > > > For SG-buffers, though, limitation makes less sense than continuous > > pages. e.g. a patch below removes the limitation for SG-buffers. > > But changing this would definitely cause the behavior difference, and > > I don't know whether it's a reasonable move -- I'm afraid that apps > > would start hogging too much memory if the limitation is gone. > > I just went through all invoking to snd_pcm_lib_preallocate_pages*(), > for those SNDRV_DMA_TYPE_DEV, some of them set the *size* equal to the > *max*, some set the *max* several times to the *size*, IMHO, the *max*s > are matched to those hardware's limiatation, comparing to the *size*s, > aren't they? > > In this case, I still think my patch hanle all > TYPE_DEV/SNDRV_DMA_TYPE_DEV/TYPE_SG/SNDRV_DMA_TYPE_DEV cases more > gracefully, we will still take the limitation from the specific driver > set, from the *max* param, and the test results looks very nice here, > we will take what the user space wanted for buffer-bytes via aply > exactly, as long as it is suitable for the interval and constraints. Well, I have a mixed feeling. Certainly we'd need some better way to allow a larger buffer allocation, especially for HDA. OTOH, if the buffer was preallocated, it's meant to be used actually. That's the point of the hw_constraint setup. And now thinking again after another cup of coffee, I wonder why we do preallocate for HDA at all. For HD-audio, the allocation of any large buffer would succeed very likely because of SG-buffer. So, just setting 0 to the preallocation size (but keeping else) would work, e.g. something like below? The help text needs adjustment, but you can see the rough idea. thanks, Takashi --- a/sound/hda/Kconfig +++ b/sound/hda/Kconfig @@ -21,9 +21,10 @@ config SND_HDA_EXT_CORE select SND_HDA_CORE config SND_HDA_PREALLOC_SIZE - int "Pre-allocated buffer size for HD-audio driver" + int "Pre-allocated buffer size for HD-audio driver" if !SND_DMA_SGBUF range 0 32768 - default 64 + default 64 if !SND_DMA_SGBUF + default 0 if SND_DMA_SGBUF help Specifies the default pre-allocated buffer-size in kB for the HD-audio driver. A larger buffer (e.g. 2048) is preferred _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org https://mailman.alsa-project.org/mailman/listinfo/alsa-devel