why did Ubuntu turn off kernel preemption in Edgy?

Johan Kiviniemi ubuntu.com-devel at johan.kiviniemi.name
Tue Nov 28 22:07:14 GMT 2006

On Tue, Nov 28, 2006 at 12:02:48PM -0500, Phillip Susi wrote:
> Karoliina Salminen wrote:
> > behind what you are playing. The ear-finger interaction don't work
> > and brains get confused and the playing gets so distracted that it
> > is easier to play without hearing anything than hearing the notes
> > coming several notes/bars behind.

> While 500ms is too long, I thought that the brain could not notice sub
> 100 ms of latency, certainly not 32 ms.

As an artist myself, i can tell a 100 ms latency is *huge*.

At 120 bpm, the length of a 32th note is 62.5 ms. There can easily be
melodies that contain such notes. The latency should be no longer than a
tiny fraction of the shortest note of the song.

As Karoliina said, it's easier to play without hearing anything than
hearing the previous note when you're already playing the next one.

Even if it's not that bad, the sense of rhythm gets confused if the
currently played note is heard with a noticeable latency.

Related to the brains' ability to notice a latency, the sense of
direction of a sound is partially based on how quickly the sound reaches
the other ear after reaching the one nearer to the source of the sound.

In air, the speed of sound is about 340 m/s. Estimating a head width of
18 cm, a sound coming from the right hand side reaches your left ear
0.53 ms later than your right ear.

Please correct me if i got my math wrong:

% units -v '4/(120/min) / 32' ms
	4/(120/min) / 32 = 62.5 ms

% units -v '18cm / (340m/s)' ms
	18cm / (340m/s) = 0.52941176 ms

Jοhan Kiviniemi  http://johan.kiviniemi.name/
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