scx_layered: per-layer log2 runqueue-latency histogram (runnable -> running)#3706
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…unning) Add a per-layer histogram of scheduling wakeup latency, measured from when a task becomes runnable to when it first starts running. This gives per-layer runqueue-latency visibility straight off the stats socket, with no external tracer. The histogram has 26 log2-us buckets. Bucket 0 is [1us, 2us) with any sub-us latency folded in. Each subsequent bucket doubles, up to the saturating tail of >= 32s. The main use case here is to provide an external scheduling engine with a way of tracking wakeup latency per layer to potentially e.g. inform whether it needs to back off and send a container to a different node if a critical layer is experiencing elevated latencies. Signed-off-by: David Vernet <void@mainfault.com>
htejun
approved these changes
Jul 17, 2026
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Add a per-layer histogram of scheduling wakeup latency, measured from
when a task becomes runnable to when it first starts running. This gives
per-layer runqueue-latency visibility straight off the stats socket,
with no external tracer.
The histogram has 26 log2-us buckets. Bucket 0 is [1us, 2us) with any
sub-us latency folded in. Each subsequent bucket doubles, up to the
saturating tail of >= 32s. The main use case here is to provide an
external scheduling engine with a way of tracking wakeup latency per
layer to potentially e.g. inform whether it needs to back off and send a
container to a different node if a critical layer is experiencing
elevated latencies.