O'Reilly Network: Low Latency in the Linux Kernel
Nov 18, 2000, 21:00 (8 Talkback[s])
(Other stories by Dave Phillips)
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"Latency can be defined as the elapsed time (delay) between the
generation of an event and its realization. If the delay is great
enough to be perceptible, you have a latency problem."
"For instance, when you play an interactive game, you expect no
delay between the initiation of an event (turning a steering wheel
or firing a weapon) and its realization (the vehicle turns when you
turn the wheel, the weapon fires when you pull the trigger). You
expect the event to occur instantaneously, or nearly so. The MIDI
keyboard to synthesizer (or soundcard) connection is another simple
example: You press the key, you expect the sound to occur
immediately. If system latency is great enough, there will be a
perceptible delay between the keypress and the resulting
"In computer systems, multimedia software and other
real-time applications are severely affected by long latency times,
but system performance at all levels can be compromised. Video and
animations suffer frame-loss, and sound applications suffer audio
dropouts. Extreme high latency may endanger data integrity during
disk read/write/copy activity. Obviously, lowering the latency
response time in a system enhances I/O through the entire system.
This is good."