On Thu, 20 Apr 2023 09:29:43 GMT, Aleksey Shipilev <sh...@openjdk.org> wrote:
>> Java API has the `Thread.sleep(millis, nanos)` method exposed to users. The >> documentation for that method clearly says the precision and accuracy are >> dependent on the underlying system behavior. However, it always rounds up >> `nanos` to 1ms when doing the actual sleep. This means users cannot do the >> micro-second precision sleeps, even when the underlying platform allows it. >> Sub-millisecond sleeps are useful to build interesting primitives, like the >> rate limiters that run with >1000 RPS. >> >> When faced with this, some users reach for more awkward APIs like >> `java.util.concurrent.locks.LockSupport.parkNanos`. The use of that API for >> sleeps is not in line with its intent, and while it "seems to work", it >> might have interesting interactions with other uses of `LockSupport`. >> Additionally, these "sleeps" are no longer visible to monitoring tools as >> "normal sleeps", e.g. as `Thread.sleep` events. Therefore, it would be >> prudent to improve current `Thread.sleep(millis, nanos)` for sub-millisecond >> granularity. >> >> Fortunately, the underlying code is almost ready for this, at least on POSIX >> side. I skipped Windows paths, because its timers are still no good. Note >> that on both Linux and MacOS timers oversleep by about 50us. I have a few >> ideas how to improve the accuracy for them, which would be a topic for a >> separate PR. >> >> Additional testing: >> - [x] New regression test >> - [x] New benchmark >> - [x] Linux x86_64 `tier1` >> - [x] Linux AArch64 `tier1` > > Aleksey Shipilev has updated the pull request incrementally with one > additional commit since the last revision: > > Handle overflows While writing the CSR, I realized we still need to keep the `MAX_SECS` cap at POSIX path for individual sleeps, if only to care for downstream Solaris ports that are still maintained. We also would like to care about accidentally calling `JavaThread::sleep(jlong millis)` with e.g. `max_jlong`. New commit should handle both. ------------- PR Comment: https://git.openjdk.org/jdk/pull/13225#issuecomment-1516018689
