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O'Reilly Network: Low Latency in the Linux Kernel

Nov 18, 2000, 21:00 (8 Talkback[s])
(Other stories by Dave Phillips)

"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 sound."

"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."

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