Luca Bruno created TS-4173:
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Summary: High latency with --enable-linux-native-aio
Key: TS-4173
URL: https://issues.apache.org/jira/browse/TS-4173
Project: Traffic Server
Issue Type: Bug
Components: Cache
Reporter: Luca Bruno
Problem:
My average disk latency on rotational disk with 10000RPM is however around 5ms.
However ATS response times, regardless of having low or high concurrent
requests, is on average 20ms.
The cause:
With --enable-linux-native-aio, the AIO period time is hardcoded to 10ms
(AIO_PERIOD in AIO.cc).
That's really suboptimal with disk latency that is lower than 10ms.
Without --enable-linux-native-aio I get on average 5ms response times which
resemble the disk read latency.
Possible solution:
Instead of waiting for 10ms unconditionally:
- Decide (don't know how yet) a number of disk ops NOPS.
- If the ops queue size >= NOPS, trigger mainAIOEvent, then reset the timer
again to AIO_PERIOD.
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