vanzin commented on a change in pull request #26058: [SPARK-10614][core] Add
monotonic time to Clock interface.
URL: https://github.com/apache/spark/pull/26058#discussion_r332714350
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File path: core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala
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@@ -288,7 +288,7 @@ private[spark] class ExecutorAllocationManager(
}
// Update executor target number only after initializing flag is unset
- updateAndSyncNumExecutorsTarget(clock.getTimeMillis())
+ updateAndSyncNumExecutorsTarget(clock.nanoTime())
Review comment:
That is interesting, but according to this:
http://btorpey.github.io/blog/2014/02/18/clock-sources-in-linux/
`CLOCK_MONOTONIC` uses RDTSC (or RDTSCP when available), which solves that
problem. The preferred one (RDTSCP) seems to be available in all modern CPUs.
So, `CLOCK_MONOTONIC` actually fulfills the requirements of the `nanoTime()`
API (that the source of time is consistent).
(The AMD K8 mentioned in your comment, which came out more than 10 years
ago, is where RDTSCP was added.)
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