[Qemu-devel] Re: [PATCH] alsaaudio: increase default buffer sizes

[malc <av1474@comtv.ru>]

On Tue, 6 May 2008, Jan Kiszka wrote:

> malc wrote:
>> On Mon, 5 May 2008, Jan Kiszka wrote:
>>
>>> malc wrote:
>>>> On Sun, 4 May 2008, Jan Kiszka wrote:
>>>>
>>>>> Jan Kiszka wrote:
>>>>>> malc wrote:
>>>>>>> On Sun, 4 May 2008, Jan Kiszka wrote:
>>>>>>>
>>>>
>>>> [..snip..]
>>>>
>>>>>>
>>>>>> Yeah, great, that was the key! Find below the version that works
>>>>>> for me
>>>>>> (on 64 bit 8) ). It even obsoletes my buffer size patch. Please merge!
>>>>>
>>>>> Declaring the buffer size tweak obsolete was too quick. I still need
>>>>> more under certain guest load, but now I'm already fine with
>>>>> DEFAULT_BUFFER_SIZE=4096. Or all in one:
>>>>
>>>> I wonder if everyone will be happy with quadrupled latency, apart from
>>>
>>> Hmm, I wonder about the scenario where this latency may actually hurt.
>>> QEMU is not /that/ fast anyway. ;)
>>
>> You would be surprised.
>
> Tell me more! :->

The only thing that i care about: DOS demos and to lesser extent old DOS
games.

>>
>>>
>>>> you and this other user on some (kvm was it) mailing list there are no
>>>> huge outcries of dissatisfaction, then again i'm not sure how many
>>>> people
>>>> use ALSA+QEMU or QEMUs+AUDIO in general.
>>>
>>> I don't think many users are actually running QEMU (or KVM) against
>>> ALSA. You have to
>>> - manually enable it during configure
>>> - pass QEMU_AUDIO_DRV=alsa (OSS remains default even if ALSA is on - I
>>>   ran into this trap first.)
>>
>> I don't see how it's a trap. You can also enable esd or fmod drivers
>> in configure along with alsa, which one should be the default?
>
> For sure, you need this mechanism with >1 audio backends being enabled
> in parallel. It's just the question how one is supposed to find out
> about this additional requirement:

Being enabled? Did you mean being built in? And what do you mean by
mechanism, mechanism to do what exactly?

> $ grep -r QEMU_AUDIO_DRV qemu
> qemu/audio/audio.c:        "  set QEMU_AUDIO_DRV=wav\n"
> qemu/audio/audio.c:        "  export QEMU_AUDIO_DRV=wav\n"
> qemu/audio/audio.c:        drvname = audio_get_conf_str ("QEMU_AUDIO_DRV", NULL, &def);
>
> Am I missing some reference? Then sorry in advance.

What is the question?

[..snip..]

>
> Well, probably configurable as well with compat-OSS (real OSS is dead on
> Linux). The fact is that - not only for me - this sharing does not work
> out-of-the-box with OSS, while it does with ALSA. Don't ask me why, I'm
> not an expert on this, I'm rather looking at it from a "normal" user
> perspective.

It doesn't with ALSA on this machine, and on the machine next to this
one, and on machine that lies on the floor. It boils down to how ALSA
was configured by distribution maintainers.

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