JDK-8227018 : CompletableFuture should not call Runtime.availableProcessors on fast path
- Type: Enhancement
- Component: core-libs
- Sub-Component: java.util.concurrent
- Affected Version: 8u191
- Priority: P3
- Status: Resolved
- Resolution: Fixed
- Submitted: 2019-07-01
- Updated: 2019-11-29
- Resolved: 2019-07-05
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| JDK 8 | Other |
|---|---|
8u241Fixed  |
openjdk8u232Fixed |
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Description
In 8u, CompletableFuture calls Runtime.availableProcessors during spin in waitingGet:
private Object waitingGet(boolean interruptible) {
...
while ((r = result) == null) {
if (spins < 0)
spins = (Runtime.getRuntime().availableProcessors() > 1) ?
1 << 8 : 0; // Use brief spin-wait on multiprocessors
Unfortunately, that falls victim to JDK-8227006, which makes it too costly. This is fixed in 9 with JDK-8134851, but that patch is too large and intrusive to backport to 8u. Therefore, we should consider backporting the small part of that patch that deals with availableProcessors handling.
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