The Case of the Extra 40ms

Re:The Case of the Extra 40ms by FpUser on Tuesday December 15, 2020 @01:45AM (#25427699)

>"A hardware interrupt is pure overhead, especially on platforms like x86 with silly interrupt latency."

Relatively speaking maybe. But I have a device I've designed that communicates to PC using interrupt transfer at the rate of 250 requests/s. I've watched it then over oscilloscope and it is stable like a rock. Sure if you overload PC it might get into trouble but it is a game like application so when the app is ran PC is not doing much else. I recently ported the same thing to Raspberry Pi 4.

[ Parent | on HN ]

Re:The Case of the Extra 40ms by amluto on Tuesday December 15, 2020 @02:10PM (#25433784)

Hah, you must never have tried this on an otherwise idle stock Sandy Bridge before Linux added mitigations :)

x86 interrupts are slow but at least reasonably consistent on a non-idle system. If your system is deeply enough into its various idle states, this is not at all true any more. I’ve seen latencies over 10ms on Sandy Bridge with C1E enabled.

[ Parent | on HN ]

Re:The Case of the Extra 40ms by FpUser on Tuesday December 15, 2020 @04:58PM (#25435754)

Linux was on Pi 4. On PC it was actually Windows. The first version went out some 7 years ago I think and was rock solid since the beginning. They must've done something right ;)

[ Parent | on HN ]