A DGX Spark keeps its cores out of deep idle
On a DGX Spark, David Heinemeier Hansson reported that the desktop felt like ~20 fps and that Speedometer 3.1 scored 10. A change merged into quattro disables every idle state past state0 on GB10.
On a DGX Spark, David Heinemeier Hansson reported that the whole desktop felt like ~20 fps, in typing, window moves and scrolling, and Speedometer 3.1 scored 10. The GPU, display link, compositor and V8 all measured fine. A change merged into quattro disables every idle state past state0 on GB10. Leaving those states takes ~300 µs or more, while the firmware table says 42/231/433 µs.
He measured a pipe round trip between two cores with a 1 ms idle gap. On a fast core the pair is 247 / 525 µs with every idle state and 11 / 16 µs on only state0.
| All idle states | Only state0 | |
|---|---|---|
| Fast core | 247 / 525 µs | 11 / 16 µs |
| Slow core | 433 / 1695 µs | 12 / 39 µs |
David Heinemeier Hansson on a DGX Spark, median and p99, with the slow-core only-state0 pair on the performance governor, in the pull request.
The slow-core only-state0 pair, 12 / 39 µs, is with the performance governor. A second slowdown, from the schedutil governor, is not in this pull request, and a GB10 still reverts to schedutil at boot. The N1x laptops are untouched. The Spark exposes no CPU power sensor, so the idle-draw increase is unknown.