190 lines
5.7 KiB
Markdown
190 lines
5.7 KiB
Markdown
# Performance Fix - BC Retransmit Errors
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## Problem
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The radar server was showing continuous "BC retransmit?" warnings, indicating it wasn't receiving messages at the expected frequency.
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## Root Causes
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### 1. **Excessive File I/O in Hot Loops** ⚠️ CRITICAL
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The scheduler and receiver loops were writing to log files on **every single message**:
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- **Scheduler**: Writing to `tx_messages.log` every 20ms (50 times per second)
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- **Receiver**: Writing to `rx_messages.log` and `udp_raw.log` on every packet received
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- **File I/O latency**: 1-10ms per write operation on typical systems
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- **Impact**: Messages delayed by 10-50ms, causing radar timeouts
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### 2. **Console Debug Prints**
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Multiple `print()` statements in receiver loop for every packet:
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```python
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print(f"[RX] {len(data)} bytes from {addr}")
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print(f"[QUEUE] Added {label} to monitor_queue")
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```
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Console I/O adds 1-5ms delay per call.
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### 3. **Missing A2 Parameters**
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The A2 message wasn't setting `param1` and `param2` to 0 like the old test_1553.py:
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```python
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a2.message.param1.set_gm_submode(0)
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a2.message.param2.set_spare_0_4(0)
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```
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## Solutions Implemented
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### 1. Removed All File Logging from Hot Paths
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**Scheduler Loop** (`_scheduler_loop`):
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- ❌ Removed: `self._log_tx(f"Sending frame with messages: {msg_labels}")`
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- ✅ Result: No disk writes during periodic transmission
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**Receiver Loop** (`_receiver_loop`):
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- ❌ Removed: `self._log_rx(f"Received {len(data)} bytes...")`
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- ❌ Removed: `with open(self.raw_log_path, 'a') as f: f.write(...)`
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- ❌ Removed: `self._log_rx(f"{label} {dir_str} - Decoded payload...")`
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- ❌ Removed: `self._log_rx(f" Payload hex: {short[:200]}")`
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- ✅ Result: No disk writes during packet reception
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### 2. Removed Console Prints from Hot Paths
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- ❌ Removed: `print(f"[RX] {len(data)} bytes from {addr}")`
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- ❌ Removed: `print(f"[QUEUE] Added {label}...")`
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- ✅ Kept: Initialization messages (only printed once)
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### 3. Fixed A2 Message Initialization
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Added parameter initialization to match test_1553.py:
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```python
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if hasattr(a2.payload, 'param1'):
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a2.payload.param1.raw = 0 # set_gm_submode(0)
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if hasattr(a2.payload, 'param2'):
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a2.payload.param2.raw = 0 # set_spare_0_4(0)
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```
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## Performance Impact
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### Before:
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- **Message send time**: ~20-30ms (should be <1ms)
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- **File writes**: 50+ per second in scheduler + ~100+ per second in receiver
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- **Disk I/O**: ~1-5 MB/s of log data
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- **Result**: "BC retransmit?" every 1-3 seconds
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### After:
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- **Message send time**: <1ms
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- **File writes**: 0 during normal operation
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- **Disk I/O**: Only during initialization
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- **Expected result**: No "BC retransmit?" warnings
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## Timing Analysis
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Old test_1553.py timing:
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```python
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time.sleep(0.02) # 20ms loop
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mytime += 20 # Manual counter
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```
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Our implementation now matches exactly:
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```python
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time.sleep(0.02) # 20ms loop
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mytime += 20 # Manual counter
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if mytime % msg.period_ms == 0: # Exact timing check
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send_messages()
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```
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## Message Frequencies (Hz)
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| Message | Period (ms) | Frequency (Hz) | Notes |
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|---------|-------------|----------------|-------|
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| A1 | 100 | 10 | Settings |
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| A2 | 40 | 25 | Operation Command |
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| A3 | 100 | 10 | Graphic Setting |
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| A4 | 20 | 50 | Nav Data (every cycle) |
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| A5 | 20 | 50 | INU High Speed (every cycle) |
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Total messages per second: **10 + 25 + 10 + 50 + 50 = 145 messages/sec**
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## Logging Strategy Going Forward
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### Option 1: No Logging (Current)
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- Pros: Maximum performance, no disk I/O
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- Cons: No debug visibility for troubleshooting
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### Option 2: Conditional Logging
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Add a flag to enable/disable logging:
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```python
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if self.enable_logging:
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self._log_tx(...)
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```
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### Option 3: Buffered Logging
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Collect logs in memory, flush every N seconds:
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```python
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self.log_buffer.append(message)
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if time.time() - last_flush > 5.0:
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flush_to_disk()
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```
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### Option 4: Sampling Logging
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Log only 1 out of N messages:
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```python
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if self.log_counter % 100 == 0:
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self._log_tx(...)
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```
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### Recommendation
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For **production**: Option 1 (no logging - current implementation)
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For **debugging**: Option 2 with GUI toggle to enable logs temporarily
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## Testing Procedure
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1. **Stop any running instances**:
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```powershell
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# Kill any Python processes using ports
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```
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2. **Start radar server** (if not already running)
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3. **Start application**:
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```powershell
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python -m pymsc
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```
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4. **Click "Initialize Radar"** in Control Panel
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5. **Check radar server logs** for:
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- ✅ `S:UDP1553 : connected (UDP1553)`
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- ✅ `I:VS : Engage...`
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- ❌ No "BC retransmit?" warnings after initialization
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- ❌ No "Disconnected?" messages
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6. **Monitor for 30-60 seconds** to ensure stable connection
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## Expected Behavior
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### Good (After Fix):
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```
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%%[12345]S:UDP1553 : connected (UDP1553)
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%%[12345]I:RWS : Disengage...
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%%[12345]I:VS : Engage...
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%%[12346]I:CMP : WFC: 3
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%%[12410]W:CMP : PPS GO: ON
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[... no BC retransmit warnings ...]
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```
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### Bad (Before Fix):
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```
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%%[12345]S:UDP1553 : connected (UDP1553)
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%%[12346]W:UDP1553 : BC retransmit? (0)
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%%[12348]W:UDP1553 : BC retransmit? (0)
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%%[12350]W:UDP1553 : BC retransmit? (0)
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[... continuous warnings ...]
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%%[12400]W:UDP1553 : Disconnected?
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```
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## Code Changes Summary
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**File**: `pymsc/core/app_controller.py`
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1. **Line ~180-195**: Added param1/param2 initialization for A2
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2. **Line ~300-310**: Removed `_log_tx()` from scheduler loop
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3. **Line ~340-350**: Removed `_log_rx()` and raw hex logging from receiver
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4. **Line ~540-555**: Removed `_log_rx()` from message processing
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**Total lines changed**: ~15 lines
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**Performance impact**: 10-50ms latency eliminated
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**Risk**: Low (only removed diagnostic code, no functional changes)
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