8a0eb77692
- One-time difficulty reset to minimum for 17 blocks at activation height - Separate RandomX build dirs for linux/win64 cross-compilation - Add build target tracking to auto-clean on target switch - Automated win64 release packaging to release-win64/ - Add build artifacts to .gitignore - Miner memory diagnostics and large-page dataset fallback
64 lines
2.5 KiB
Markdown
64 lines
2.5 KiB
Markdown
# Changelog: RandomX Mining Optimization
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## Summary
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Optimizes RandomX miner memory usage by replacing per-thread dataset/cache allocation with a shared `RandomXDatasetManager`. Reduces memory footprint from ~2.3GB × N threads to ~2.3GB total.
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## Problem
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The original RandomX miner implementation allocated a full RandomX dataset (~2GB) and cache (~256MB) for each mining thread. With multiple threads, this quickly exhausted available memory:
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- 4 threads: ~9.2GB
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- 8 threads: ~18.4GB
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- 16 threads: ~36.8GB
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## Solution
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Implemented a shared `RandomXDatasetManager` that allocates a single dataset and cache, shared by all miner threads via read-only access (explicitly supported by RandomX design).
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## Changes
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### `src/miner.cpp`
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- **Added `RandomXDatasetManager` class:**
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- Manages a single shared RandomX cache and dataset.
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- Thread-safe key updates using `boost::shared_mutex` (readers-writer lock).
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- `Initialize(key)`: Allocates cache and dataset, initializes with key, builds dataset using all CPU cores.
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- `UpdateKey(newKey)`: Acquires exclusive lock, reinitializes cache with new key, rebuilds dataset.
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- `GetDataset()`: Returns pointer to shared dataset for VM creation.
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- `AcquireSharedLock()` / `ReleaseSharedLock()`: Miner threads hold shared lock while hashing to prevent key updates mid-hash.
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- `Shutdown()`: Releases all RandomX resources.
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- **Modified `GenerateBitcoins()`:**
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- Initializes `RandomXDatasetManager` with initial key before spawning miner threads.
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- Calls `Shutdown()` when mining stops.
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- **Modified `RandomXMiner()`:**
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- Creates lightweight per-thread VM using shared dataset (`randomx_create_vm(..., manager.GetDataset())`).
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- Acquires shared lock before hashing, releases after.
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- On key rotation: releases shared lock, calls `manager.UpdateKey()`, reacquires shared lock, recreates VM.
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- Cleanup only destroys thread's VM — dataset/cache owned by manager.
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## Memory Usage
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| Threads | Before | After |
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|---------|--------|-------|
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| 1 | ~2.3GB | ~2.3GB |
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| 4 | ~9.2GB | ~2.3GB |
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| 8 | ~18.4GB | ~2.3GB |
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| 16 | ~36.8GB | ~2.3GB |
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## Thread Safety
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- RandomX dataset is read-only after initialization — safe to share across threads.
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- `boost::shared_mutex` ensures:
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- Multiple threads can hash concurrently (shared lock).
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- Key updates are exclusive (exclusive lock blocks until all shared locks release).
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- No thread hashes with stale dataset during key change.
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## Files Modified
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| File | Lines Added | Lines Removed |
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|------|-------------|---------------|
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| `src/miner.cpp` | ~80 | ~20 |
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