Core performance¶

Measure the complete application path before changing socket options. Message size, connection count, queue depth, transport, and TLS all affect throughput and latency.

Backpressure and HWM¶

Send and receive HWM values limit the queued bytes. Automatic HWM uses the socket pattern, configured profile, per-message byte input, and connection count to select bounded queue values. Inspect the applied plan through zlink_monitor_status().

Use COMPACT when memory is constrained, BALANCED for general workloads, and THROUGHPUT only when the additional queue memory is acceptable. A send-ready notification means retrying is worthwhile; it does not guarantee that the next send succeeds.

Memory and descriptors¶

Budget both idle connection cost and queued-message peaks. Set RLIMIT_NOFILE from the expected connection count plus operational headroom. ZLINK_MAX_SOCKETS limits socket handles, not transport connections.

Benchmark procedure¶

Rebuild core/build after changing Core sources. The benchmark runner must print the exact libzlink path and reject a runtime older than the sources. Record message size, connection count, duration, transport, TLS setting, HWM profile, CPU allocation, and the reported percentile statistics.