Performance Notes

Sources:

• Documentation/source/PERFORMANCE_FIXES_SUMMARY.md
• Documentation/source/BUFFER_SIZE_ANALYSIS.md
• Documentation/source/GETVALUES_PERFORMANCE_ANALYSIS.md
• Documentation/source/GRACEFUL_SHUTDOWN_FIX.md

Critical Fix: TCP_NODELAY on Protocol Client

Problem

The ProtocolServer/ProtocolClient RPC implementation was experiencing sporadic 100–200 ms delays caused by Nagle's algorithm batching small TCP packets.

Root Cause

Fix Applied

In ProtocolClient.OnConnected():

Socket.NoDelay          = true;     // CRITICAL — disables Nagle's algorithm
Socket.ReceiveBufferSize = 32768;   // 32 KB
Socket.SendBufferSize    = 32768;   // 32 KB
Socket.ReceiveTimeout    = 5000;    // 5 s
Socket.SendTimeout       = 5000;    // 5 s

Same settings applied to ProtocolSession.OnConnected() (buffers/timeouts were new there).

Connection loop changed from Thread.Yield() (tight spin) to Thread.Sleep(10) to reduce CPU during connection establishment.

TCP Buffer Sizing

Application-Level Buffers (ProtocolReceiver)

OS-Level Socket Buffers

Both sides are now explicitly set to 32 KB — optimised for typical message sizes of 250–2 100 bytes.

Packet Wire Format

[SOF(1)] + [MAGIC(4)] + [GUID(36)] + [Base64Data] + [EOF(1)]
= 42 bytes fixed overhead + Base64-encoded payload

Base64 inflates binary payload by ~33%:

TotalPacketSize = 42 + ceil(PayloadSize / 3) × 4

Typical sizes: | Call type | Serialized | On wire | |-----------|-----------|---------| | Simple (1–2 params) | 136–356 bytes | 250–550 bytes | | Medium (5–10 params) | 500–1 500 bytes | 750–2 100 bytes |

GetValues() Performance Call Stack

The full round-trip for a ResourceValuesProxy.GetValues(string[] names) call:

Client:
  1. CreateMethodCall()
  2. Serialize → Base64 encode → send TCP packet

Network:
  3. TCP/IP transmission

Server:
  4. ProtocolSession receives packet
  5. Deserialize ReflectionCall
  6. Invoke GetValues() via compiled delegate (reflection is cached)
  7. Serialize response → Base64 → send TCP packet

Client:
  8. Receive packet, deserialize ReflectionProperties
  9. Return result to caller

Instrumented Warning Thresholds

If you see consistent warnings above these thresholds, check:

1. Socket.NoDelay = true on both sides (see above)
2. Network round-trip latency (ping <device>)
3. Server-side GetValues() implementation for lock contention

WebApi GetValues Performance

The HTTP WebApi (/api/resources/values/get) batches multiple resource reads in a single HTTP round-trip. Prefer batch reads over individual reads when fetching multiple values:

// ✗ N round-trips
foreach (var name in names)
    values[name] = await client.Resources.GetValueAsync(name);

// ✓ 1 round-trip
var values = await client.Resources.GetValuesAsync(names);