Cyclotron

Cyclotron is a performance model for the Radiance GPU architecture. It has a functional RISC-V SIMT simulator, and a timing layer that runs on top of it.

Usage

Building

cargo build --release

Basic execution (functional only)

cargo run --release -- config.toml

Or with a specific binary:

cargo run --release -- config.toml --binary-path path/to/kernel.elf

With timing model enabled

cargo run --release -- config.toml --timing

cargo run --release -- config.toml --binary-path path/to/kernel.elf --timing

CYCLOTRON_GRAPH_LOG=1 cargo run --release -- config.toml --timing --binary-path  path/to/kernel.elf

Common CLI options

| Option | Description | |--------|-------------| | --timing | Enable the timing model | | --binary-path <path> | Override the ELF binary to run | | --num-lanes <N> | Override lanes per warp (default: 16) | | --num-warps <N> | Override warps per core (default: 4) | | --num-cores <N> | Override cores per cluster (default: 1) | | --log <level> | Log level: 0=none, 1=info, 2=debug | | --gen-trace <bool> | Generate instruction trace |

Example: Run ISA tests

./test/run-isa-tests.sh

Example: Run microbenchmarks with timing

./test/run-microbench-tests.sh

Performance Logging

When the timing model is enabled, Cyclotron automatically writes performance logs to performance_logs/run_<timestamp>_<pid>/.

Environment variables

| Variable | Description | |----------|-------------| | CYCLOTRON_PERF_LOG_DIR | Override the base directory for logs (default: performance_logs/) | | CYCLOTRON_GRAPH_LOG=1 | Enable detailed backpressure event logging |

Output files

Each run directory contains:

| File | Description | |------|-------------| | summary.json | End-of-run aggregate statistics — the primary output. Contains per-core and total metrics for scheduler utilization, cache hit rates, memory latencies, SMEM bank conflicts, LSU statistics, and more. | | stats.jsonl | Per-cycle statistics stream. Each line is a snapshot of core performance counters at a given cycle. | | graph_backpressure.jsonl | Backpressure events (only if CYCLOTRON_GRAPH_LOG=1). Logs every rejected request in the FlowGraph: which edge, source/destination nodes, rejection reason, retry cycle, and queue capacity. |

Timing parameters are modular — see config/timing/ for individual component configurations (cache sizes, queue depths, latencies, etc.).