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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3436DC36010 for ; Fri, 4 Apr 2025 07:06:05 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1u0b76-0005CF-Vg; Fri, 04 Apr 2025 03:05:17 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1u0b75-00059w-1G for qemu-devel@nongnu.org; Fri, 04 Apr 2025 03:05:15 -0400 Received: from kylie.crudebyte.com ([5.189.157.229]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1u0b73-00080A-6j for qemu-devel@nongnu.org; Fri, 04 Apr 2025 03:05:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=kylie; h=Content-Type:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Content-ID:Content-Description; bh=29wKsr6PKXjiqbb6t5bEUy/E6kXF5llH9Mk8UWhAUnI=; b=Y4cU98iWug/RFLfN29Lykg4asu Shmlir7bwhnH1yEmZBUmk/8lYEoEIolNNHrPBFyMWRp5v6ypam9zO/C5tFGGB9VJo7th32Wzzu2cW 5Qc42XL6RMtBI9BkmHn+uU0Qjp1xQMLPyfXotDQvbVPtbzFUbfbkr1iwM82YQpV7gzRThwFxcscc1 XvT+8Nkbcb5W7B8Refe27iMUgtrbc2SBBrfrNk16fb9FQAk1GgJi1TL8kis1e0rnvqCOkR+oQ11Fs TqiWssaqdtRfqCp9G3VTzjPY9YCf9VThoEWbfXIywAVXl0W+a7AAMcIPAF/lo9dJqDhYGLt0NRWeZ McST38/HVPz8CUtghlEB3JoqevXMvOVIZVK/I/ul6T2F3ldDTX2iTGEK1YfujhhTQSIelnJastPaP YuLyDYFnF88rBD0lqfSwvMJhahAlPyILgNCcp/8wXcgYM+XkxEb3Bvws+LuY1WpfzRRpzIWotwOZW nLGsdNaDeFIPe/6sJQAf8MPEpLIn7VGGgEqLHiOjUpY41FlSa19M27v6eUdUCfEyt1Y36RkIAcZVG eOwlsavobQOxqcOCHVjLIRacRD4qYPQK7C99HrVJSkavTbb7PNuBoHCy3fdFVQ5nFSb/0L8FmoBaK TDJNOhuiYUt5VzyJys6tw/j/7fyVjTCwBuzYqbVuM=; From: Christian Schoenebeck To: qemu-devel@nongnu.org, Volker Ruemelin Cc: Gerd Hoffmann , BALATON Zoltan Subject: Re: [PATCH] alsaaudio: Set try-poll to false by default Date: Fri, 04 Apr 2025 09:05:08 +0200 Message-ID: <37909074.vkC8U9mzk0@silver> In-Reply-To: References: <20250316002046.D066A4E6004@zero.eik.bme.hu> <2118992.kbFERA6akJ@silver> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Received-SPF: pass client-ip=5.189.157.229; envelope-from=qemu_oss@crudebyte.com; helo=kylie.crudebyte.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Monday, March 31, 2025 3:05:24 PM CEST BALATON Zoltan wrote: > On Sun, 23 Mar 2025, Christian Schoenebeck wrote: > > On Sunday, March 16, 2025 1:20:46 AM CET BALATON Zoltan wrote: > >> Quoting Volker R=FCmelin: "try-poll=3Don tells the ALSA backend to try= to > >> use an event loop instead of the audio timer. This works most of the > >> time. But the poll event handler in the ALSA backend has a bug. For > >> example, if the guest can't provide enough audio frames in time, the > >> ALSA buffer is only partly full and the event handler will be called > >> again and again on every iteration of the main loop. This increases > >> the processor load and the guest has less processor time to provide > >> new audio frames in time. I have two examples where a guest can't > >> recover from this situation and the guest seems to hang." > >> > >> One reproducer I've found is booting MorphOS demo iso on > >> qemu-system-ppc -machine pegasos2 -audio alsa which should play a > >> startup sound but instead it freezes. Even when it does not hang it > >> plays choppy sound. Volker suggested using command line to set > >> try-poll=3Doff saying: "The try-poll=3Doff arguments are typically > >> necessary, because the alsa backend has a design issue with > >> try-poll=3Don. If the guest can't provide enough audio frames, it's > >> really unhelpful to ask for new audio frames on every main loop > >> iteration until the guest can provide enough audio frames. Timer based > >> playback doesn't have that problem." > >> > >> But users cannot easily find this option and having a non-working > >> default is really unhelpful so to make life easier just set it to > >> false by default which works until the issue with the alsa backend can > >> be fixed. > >> > >> Signed-off-by: BALATON Zoltan > >> --- > >> This fixes my issue but if somebody has a better fix I'm open to that > >> too. > >> > >> audio/alsaaudio.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/audio/alsaaudio.c b/audio/alsaaudio.c > >> index cacae1ea59..9b6c01c0ef 100644 > >> --- a/audio/alsaaudio.c > >> +++ b/audio/alsaaudio.c > >> @@ -899,7 +899,7 @@ static void alsa_enable_in(HWVoiceIn *hw, bool ena= ble) > >> static void alsa_init_per_direction(AudiodevAlsaPerDirectionOptions *= apdo) > >> { > >> if (!apdo->has_try_poll) { > >> - apdo->try_poll =3D true; > >> + apdo->try_poll =3D false; > >> apdo->has_try_poll =3D true; > >> } > >> } > >> > > > > Correct me if I am wrong, but AFAICS if polling is not used then no sta= te > > changes would be handled, no? At least I don't see any snd_pcm_state() = call > > outside of alsa_poll_handler(). >=20 > I have no idea but this fixes the problem (and does the same that can be= =20 > also done from command line but nobody can find that command line option)= =20 > so unless somebody has a better idea could this be merged as a fix for=20 > now? Well, I understand that if fixes the misbehaviour you encountered. But how helpful would it be if it then breaks behaviour for other people instead? I think it would be better to add a 2nd patch that would handle state chang= es in callback mode. That would satisfy both groups of people. AFAICS snd_pcm_state() can be called both in polling mode and callback mode. Just my 2 cents. Of course it's up to Gerd to decide. /Christian