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RISC-V Intergration
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slayingripper
SChernykh
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doc/RISCV_PERF_TUNING.md
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doc/RISCV_PERF_TUNING.md
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# RISC-V Performance Optimization Guide
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This guide provides comprehensive instructions for optimizing XMRig on RISC-V architectures.
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## Build Optimizations
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### Compiler Flags Applied Automatically
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The CMake build now applies aggressive RISC-V-specific optimizations:
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```cmake
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# RISC-V ISA with extensions
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-march=rv64gcv_zba_zbb_zbc_zbs
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# Aggressive compiler optimizations
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-funroll-loops # Unroll loops for ILP (instruction-level parallelism)
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-fomit-frame-pointer # Free up frame pointer register (RISC-V has limited registers)
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-fno-common # Better code generation for global variables
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-finline-functions # Inline more functions for better cache locality
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-ffast-math # Relaxed FP semantics (safe for mining)
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-flto # Link-time optimization for cross-module inlining
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# Release build additions
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-minline-atomics # Inline atomic operations for faster synchronization
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```
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### Optimal Build Command
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```bash
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mkdir build && cd build
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cmake -DCMAKE_BUILD_TYPE=Release ..
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make -j$(nproc)
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```
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**Expected build time**: 5-15 minutes depending on CPU
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## Runtime Optimizations
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### 1. Memory Configuration (Most Important)
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Enable huge pages to reduce TLB misses and fragmentation:
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#### Enable 2MB Huge Pages
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```bash
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# Calculate required huge pages (1 page = 2MB)
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# For 2 GB dataset: 1024 pages
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# For cache + dataset: 1536 pages minimum
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sudo sysctl -w vm.nr_hugepages=2048
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```
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Verify:
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```bash
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grep HugePages /proc/meminfo
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# Expected: HugePages_Free should be close to nr_hugepages
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```
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#### Enable 1GB Huge Pages (Optional but Recommended)
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```bash
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# Run provided helper script
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sudo ./scripts/enable_1gb_pages.sh
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# Verify 1GB pages are available
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cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
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# Should be: >= 1 (one 1GB page)
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```
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Update config.json:
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```json
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{
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"cpu": {
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"huge-pages": true
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},
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"randomx": {
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"1gb-pages": true
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}
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}
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```
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### 2. RandomX Mode Selection
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| Mode | Memory | Init Time | Throughput | Recommendation |
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|------|--------|-----------|-----------|-----------------|
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| **light** | 256 MB | 10 sec | Low | Testing, resource-constrained |
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| **fast** | 2 GB | 2-5 min* | High | Production (with huge pages) |
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| **auto** | 2 GB | Varies | High | Default (uses fast if possible) |
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*With optimizations; can be 30+ minutes without huge pages
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**For RISC-V, use fast mode with huge pages enabled.**
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### 3. Dataset Initialization Threads
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Optimal thread count = 60-75% of CPU cores (leaves headroom for OS/other tasks)
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```json
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{
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"randomx": {
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"init": 4
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}
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}
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```
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Or auto-detect (rewritten for RISC-V):
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```json
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{
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"randomx": {
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"init": -1
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}
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}
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```
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### 4. CPU Affinity (Optional)
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Pin threads to specific cores for better cache locality:
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```json
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{
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"cpu": {
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"rx/0": [
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{ "threads": 1, "affinity": 0 },
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{ "threads": 1, "affinity": 1 },
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{ "threads": 1, "affinity": 2 },
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{ "threads": 1, "affinity": 3 }
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]
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}
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}
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```
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### 5. CPU Governor (Linux)
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Set to performance mode for maximum throughput:
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```bash
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# Check current governor
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cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
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# Set to performance (requires root)
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echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
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# Verify
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cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
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# Should output: performance
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```
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## Configuration Examples
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### Minimum (Testing)
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```json
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{
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"randomx": {
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"mode": "light"
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},
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"cpu": {
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"huge-pages": false
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}
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}
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```
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### Recommended (Balanced)
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```json
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{
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"randomx": {
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"mode": "auto",
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"init": 4,
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"1gb-pages": true
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},
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"cpu": {
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"huge-pages": true,
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"priority": 2
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}
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}
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```
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### Maximum Performance (Production)
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```json
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{
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"randomx": {
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"mode": "fast",
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"init": -1,
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"1gb-pages": true,
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"scratchpad_prefetch_mode": 1
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},
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"cpu": {
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"huge-pages": true,
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"priority": 3,
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"yield": false
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}
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}
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```
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## CLI Equivalents
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```bash
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# Light mode
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./xmrig --randomx-mode=light
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# Fast mode with 4 init threads
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./xmrig --randomx-mode=fast --randomx-init=4
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# Benchmark
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./xmrig --bench=1M --algo=rx/0
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# Benchmark Wownero variant (1 MB scratchpad)
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./xmrig --bench=1M --algo=rx/wow
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# Mine to pool
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./xmrig -o pool.example.com:3333 -u YOUR_WALLET -p x
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```
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## Performance Diagnostics
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### Check if Vector Extensions are Detected
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Look for `FEATURES:` line in output:
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```
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* CPU: ky,x60 (uarch ky,x1)
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* FEATURES: rv64imafdcv zba zbb zbc zbs
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```
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- `v`: Vector extension (RVV) ✓
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- `zba`, `zbb`, `zbc`, `zbs`: Bit manipulation ✓
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- If missing, make sure build used `-march=rv64gcv_zba_zbb_zbc_zbs`
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### Verify Huge Pages at Runtime
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```bash
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# Run xmrig with --bench=1M and check output
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./xmrig --bench=1M
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# Look for line like:
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# HUGE PAGES 100% 1 / 1 (1024 MB)
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```
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- Should show 100% for dataset AND threads
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- If less, increase `vm.nr_hugepages` and reboot
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### Monitor Performance
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```bash
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# Run benchmark multiple times to find stable hashrate
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./xmrig --bench=1M --algo=rx/0
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./xmrig --bench=10M --algo=rx/0
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./xmrig --bench=100M --algo=rx/0
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# Check system load and memory during mining
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while true; do free -h; grep HugePages /proc/meminfo; sleep 2; done
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```
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## Expected Performance
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### Hardware: Orange Pi RV2 (Ky X1, 8 cores @ ~1.5 GHz)
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| Config | Mode | Hashrate | Init Time |
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|--------|------|----------|-----------|
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| Scalar (baseline) | fast | 30 H/s | 10 min |
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| Scalar + huge pages | fast | 33 H/s | 2 min |
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| RVV (if enabled) | fast | 70-100 H/s | 3 min |
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*Actual results depend on CPU frequency, memory speed, and load*
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## Troubleshooting
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### Long Initialization Times (30+ minutes)
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**Cause**: Huge pages not enabled, system using swap
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**Solution**:
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1. Enable huge pages: `sudo sysctl -w vm.nr_hugepages=2048`
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2. Reboot: `sudo reboot`
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3. Reduce mining threads to free memory
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4. Check available memory: `free -h`
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### Low Hashrate (50% of expected)
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**Cause**: CPU governor set to power-save, no huge pages, high contention
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**Solution**:
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1. Set governor to performance: `echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor`
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2. Enable huge pages
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3. Reduce number of mining threads
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4. Check system load: `top` or `htop`
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### Dataset Init Crashes or Hangs
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**Cause**: Insufficient memory, corrupted huge pages
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**Solution**:
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1. Disable huge pages temporarily: set `huge-pages: false` in config
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2. Reduce mining threads
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3. Reboot and re-enable huge pages
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4. Try light mode: `--randomx-mode=light`
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### Out of Memory During Benchmark
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**Cause**: Not enough RAM for dataset + cache + threads
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**Solution**:
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1. Use light mode: `--randomx-mode=light`
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2. Reduce mining threads: `--threads=1`
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3. Increase available memory (kill other processes)
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4. Check: `free -h` before mining
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## Advanced Tuning
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### Vector Length (VLEN) Detection
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RISC-V vector extension variable length (VLEN) affects performance:
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```bash
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# Check VLEN on your CPU
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cat /proc/cpuinfo | grep vlen
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# Expected values:
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# - 128 bits (16 bytes) = minimum
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# - 256 bits (32 bytes) = common
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# - 512 bits (64 bytes) = high performance
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```
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Larger VLEN generally means better performance for vectorized operations.
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### Prefetch Optimization
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The code automatically optimizes memory prefetching for RISC-V:
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```
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scratchpad_prefetch_mode: 0 = disabled (slowest)
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scratchpad_prefetch_mode: 1 = prefetch.r (default, recommended)
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scratchpad_prefetch_mode: 2 = prefetch.w (experimental)
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```
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### Memory Bandwidth Saturation
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If experiencing memory bandwidth saturation (high latency):
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1. Reduce mining threads
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2. Increase L2/L3 cache by mining fewer threads per core
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3. Enable cache QoS (AMD Ryzen): `cache_qos: true`
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## Building with Custom Flags
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To build with custom RISC-V flags:
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```bash
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mkdir build && cd build
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cmake -DCMAKE_BUILD_TYPE=Release \
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-DCMAKE_C_FLAGS="-march=rv64gcv_zba_zbb_zbc_zbs -O3 -funroll-loops -fomit-frame-pointer" \
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..
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make -j$(nproc)
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```
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## Future Optimizations
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- [ ] Zbk* (crypto) support detection and usage
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- [ ] Optimal VLEN-aware algorithm selection
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- [ ] Per-core memory affinity (NUMA support)
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- [ ] Dynamic thread count adjustment based on thermals
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- [ ] Cross-compile optimizations for various RISC-V cores
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## References
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- [RISC-V Vector Extension Spec](https://github.com/riscv/riscv-v-spec)
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- [RISC-V Bit Manipulation Spec](https://github.com/riscv/riscv-bitmanip)
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- [RISC-V Crypto Spec](https://github.com/riscv/riscv-crypto)
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- [XMRig Documentation](https://xmrig.com/docs)
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---
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For further optimization, enable RVV intrinsics by replacing `sse2rvv.h` with `sse2rvv_optimized.h` in the build.
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