Forty Milliseconds Exactly
An RPC client on an established, idle connection issues two write() calls per request: 4 bytes of length prefix, then a 96 byte body. The server parses the length, reads the body, and only then replies.
Measured client-side latency over an hour on a 0.4 ms LAN:
| percentile | latency |
|---|---|
| p50 | 0.4 ms |
| p90 | 0.4 ms |
| p99 | 40.1 ms |
| p99.9 | 40.2 ms |
There are zero retransmissions in the capture and zero packet loss on the switch counters. What produces the 40 ms cliff?
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