netty5/common
Carl Mastrangelo 1dff107de1 Don't re-arm timerfd each epoll_wait (#7816)
Motivation:
The Epoll transport checks to see if there are any scheduled tasks
before entering epoll_wait, and resets the timerfd just before.
This causes an extra syscall to timerfd_settime before doing any
actual work.   When scheduled tasks aren't added frequently, or
tasks are added with later deadlines, this is unnecessary.

Modification:
Check the *deadline* of the peeked task in EpollEventLoop, rather
than the *delay*.  If it hasn't changed since last time, don't
re-arm the timer

Result:
About 2us faster on gRPC RTT 50pct latency benchmarks.

Before (2 runs for 5 minutes, 1 minute of warmup):

```
50.0%ile Latency (in nanos):		64267
90.0%ile Latency (in nanos):		72851
95.0%ile Latency (in nanos):		78903
99.0%ile Latency (in nanos):		92327
99.9%ile Latency (in nanos):		119691
100.0%ile Latency (in nanos):		13347327
QPS:                           14933

50.0%ile Latency (in nanos):		63907
90.0%ile Latency (in nanos):		73055
95.0%ile Latency (in nanos):		79443
99.0%ile Latency (in nanos):		93739
99.9%ile Latency (in nanos):		123583
100.0%ile Latency (in nanos):		14028287
QPS:                           14936
```

After:
```
50.0%ile Latency (in nanos):		62123
90.0%ile Latency (in nanos):		70795
95.0%ile Latency (in nanos):		76895
99.0%ile Latency (in nanos):		90887
99.9%ile Latency (in nanos):		117819
100.0%ile Latency (in nanos):		14126591
QPS:                           15387

50.0%ile Latency (in nanos):		61021
90.0%ile Latency (in nanos):		70311
95.0%ile Latency (in nanos):		76687
99.0%ile Latency (in nanos):		90887
99.9%ile Latency (in nanos):		119527
100.0%ile Latency (in nanos):		6351615
QPS:                           15571
```
2018-09-11 13:38:38 +02:00
..
src Don't re-arm timerfd each epoll_wait (#7816) 2018-09-11 13:38:38 +02:00
pom.xml [maven-release-plugin] prepare for next development iteration 2018-08-24 06:36:33 +00:00