Re: [ecasound] I JUST KILLED A HARDRIVE WITH ECASOUND

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Subject: Re: [ecasound] I JUST KILLED A HARDRIVE WITH ECASOUND
From: Kai Vehmanen (k@eca.cx)
Date: Fri May 26 2000 - 18:44:25 EEST

On Thu, 25 May 2000, Jeremy Hall wrote:

> I chose a buffer size of 1 because I didn't want latency between the
> channels and the loops. My kernel has the lowlatency patches installed,
> and it set to work mixing the channels down.

This is a very bad idea. With -b:1, all cpu-time is wasted on context
switches and buffering overhead. And it's impossible to get this
low latency - at least with normal PCs. Pro-level digital recording
systems reach latencies of 2-3ms. That means -b:64 -> -b:128 in
ecasound terms. To get better latencies, you need special hardware.

###| /empty1 |$ time ecasound -i track04.wav -o null -q
6.52user 0.20system 0:06.72elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (5609major+200minor)pagefaults 0swaps

###| /empty1 |$ time ecasound -i track04.wav -o null -q -b:4096
(eca-chainsetup) Setting buffersize to (samples) 4096.
6.85user 0.39system 0:07.23elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (689major+219minor)pagefaults 0swaps

###| /empty1 |$ time ecasound -i track04.wav -o null -q -b:1
(eca-chainsetup) Setting buffersize to (samples) 1.
50.46user 0.22system 0:50.68elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (689major+186minor)pagefaults 0swaps

As you can see, -b:1 makes ecasound _really_ slow.

> and THAT was all that happened. Some processes that were running still
> ran from memory, but when I went down a few hours later to hit the reset
[...]
> DON'T DO THIS AT HOME, IT IS FATAL
> MAN, how could this happen?

Hmm, ecasound doesn't have any lowlevel stuff (no asm, no direct
kernel hacks, etc), so it can't break your hardware. Streaming multimedia,
however, is heavy on the harddisks. If they're about to fail,
doing heavy-i/o is always risky. 

-- 
Kai Vehmanen <k@eca.cx> ---------------- CS, University of Turku .
 . audio software for linux .. http://www.eca.cx 		 .
 . armchair-tunes mp3/wav/ra . http://www.wakkanet.fi/sculpscape .

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