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Capturing a trace with
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version: "1.0.1" name: systing-trace description: Capture a Linux system trace with systing. Use when the user wants to profile, trace, or record system activity (scheduling, stacks, network, memory, syscalls, Python stacks, TPU ops/metrics) into a DuckDB or Perfetto file. Guides correct invocation of the systing binary as root, choosing recorders, targeting PIDs/cgroups/commands, and output formats.
Capturing a trace with systing
systing is a BPF-based Linux tracer. It captures scheduling events, IRQs, stack traces, network activity, memory events, syscalls, and more into a DuckDB database (or Perfetto trace) for later analysis.
Prerequisites
- Must run as root, or hold
CAP_BPF+CAP_PERFMON(CAP_SYS_ADMINalso works). Usesudo. - Output: prefer
--output foo.duckdbfor analysis with thesysting-analyzeMCP server. The default is `trace.pb` (Perfetto), so always pass--outputexplicitly when you want DuckDB.
Common invocations
Trace a command from start to finish
bash
sudo systing --output trace.duckdb -- python3 myscript.py
Everything after -- is the command. Only the command, its threads, and children are traced.
Trace an existing PID for N seconds
bash
sudo systing -p <PID> -d 10 --output trace.duckdb
Trace a cgroup
bash
sudo systing -c /sys/fs/cgroup/my.slice -d 30 --output trace.duckdb
System-wide trace (no PID/cgroup filter)
bash
sudo systing -d 5 --output trace.duckdb
-d 0 (the default) means "run until Ctrl-C, or until the -- command exits".
Recorders (what to capture)
List available recorders and their defaults:
bash
systing --list-recorders
| Recorder | Default | Captures | |
|---|---|---|---|
sched | on | Scheduler events (context switches, wakeups, runqueue) | |
irq | on | IRQ and softirq events (irq_handler_*, softirq_*) | |
cpu-stacks | on | On-CPU perf stack samples | |
sleep-stacks | on | Uninterruptible sleep (D-state) stacks | |
interruptible-stacks | on | Interruptible sleep (S-state) stacks | |
syscalls | off | All syscall entry/exit (raw_syscalls:sys_enter/sys_exit) | |
network | off | Base network recorder: socket/TCP connection state tracking | |
network-syscalls | off | Network syscall-level tracing (send/recv bytes, buffer fill, stalls) — no per-packet probes | |
network-packets | off | Packet-level tracing (sendmsg, recvmsg, qdisc, drops, retransmits, RTT) | |
memory | off | RSS tracking, mmap/munmap/brk, page faults | |
memory-alloc | off | Heap allocator uprobes (malloc/calloc/realloc/free) with stacks | |
markers | off | Userspace marker events (faccessat2 with mode=-975) | |
tpu | off | TPU op-level profile via XLA runtime gRPC (port 8466) | |
tpu-metrics | off | TPU runtime metrics polling (port 8431, lightweight) |
Enable extras with --add-recorder:
bash
sudo systing --add-recorder network --add-recorder syscalls -d 10 --output trace.duckdb
Or restrict to only specific recorders with --only-recorder (disables every default first):
bash
sudo systing --only-recorder sched --only-recorder network -d 10 --output trace.duckdb
Recorder dependencies and companions
--add-recorder networkalso enables `network-packets` (the common investigation shape).--only-recorder networkis state-only: connection/state tracking with no per-packet kprobes.network-packetsandnetwork-syscallseach require the basenetworkrecorder and enable it implicitly.memory-allocrequires and implicitly enablesmemory.- Recorders that are on by default can also be turned off directly:
--no-sched,--no-irq,--no-cpu-stack-traces,--no-sleep-stack-traces,--no-interruptible-stack-traces,-n/--no-stack-traces(all stacks).
Key options
Targeting and duration
| Flag | Purpose | |
|---|---|---|
-p, --pid <PID> | Target a specific process (repeatable) | |
-c, --cgroup <CGROUP> | Target a cgroup path | |
-d, --duration <SEC> | Duration in seconds (default 0 = until Ctrl-C or command exits) | |
--continuous <SEC> | Rolling-window mode: keep only the last <SEC> seconds in the ring buffers. Cannot be combined with a -- <command> | |
-v, --verbose | Increase verbosity (repeatable) |
Output
| Flag | Purpose | |
|---|---|---|
--output <PATH> | Output file, format from extension: .duckdb, .pb/.perfetto, .systing/.systing.gz (profile export, see docs/PROFILE_EXPORT_FORMAT.md). Default trace.pb | |
--output-dir <DIR> | Directory for intermediate parquet files (default ./traces) | |
--parquet-only | Skip final trace generation, keep only the parquet files | |
--stream <URI> | Stream parquet over a socket instead of writing to disk: vsock://CID:PORT, unix:///path.sock, tcp://host:port (tcp is unauthenticated — trusted networks only) |
Sampling and counters
| Flag | Purpose | |
|---|---|---|
--sample-freq <HZ> | CPU stack-sampling rate per CPU (default 1000). Fixed-period mode: exact with --sw-event, and the rate at max CPU frequency for cpu-cycles | |
-s, --sw-event | Use a software clock event for sampling (VMs without a PMU) | |
--perf-counter <NAME> | Sample a hardware/software counter, e.g. instructions, cycles, topdown* (repeatable) | |
--cpu-frequency | Record CPU frequency tracks |
Symbolization
| Flag | Purpose | |
|---|---|---|
--collect-pystacks | Resolve Python frames in user stacks | |
--pystacks-debug | Debug output for Python stack tracing | |
--enable-debuginfod | Better symbol resolution (requires DEBUGINFOD_URLS) | |
--collect-build-id | Store user frames as (build-id, file offset) so exited processes stay symbolizable offline | |
--symbolize-names-only | ELF symbol tables only — no DWARF, no line info, no inline frames. Bounds symbolization memory on hosts with many debug binaries | |
--symbolize-elide-generics | Collapse generic/template args in symbol names longer than 256 bytes | |
--no-frame-labels | Render unsymbolized frames as bare hex instead of contextual labels | |
--no-gopclntab | Don't symbolize stripped Go binaries from .gopclntab | |
--no-gvisor-guest-maps | Don't query gVisor sandboxes' control sockets for guest maps |
Memory recorder tuning
| Flag | Purpose | |
|---|---|---|
--memory-fault-sample-rate <N> | Sample 1 in N user page faults (default 97; 0/1 = all) | |
--memory-rss-threshold-bytes <N> | Min byte drift between rss_stat events (default max(16 MiB, 64*nr_cpus*page_size); 0 = every event) | |
--memory-alloc-sample-rate <N> | Sample 1 in N allocator calls (default 1). Values > 1 sample alloc/free independently, so alloc/free pairing for leak detection is unreliable — hotspot profiling only | |
--memory-alloc-lib <LIB> | Override allocator library. Absolute path = host namespace verbatim; bare name resolved per-pid via /proc/<pid>/maps | |
--memory-alloc-symbol-prefix <P> | Prefix for malloc/free symbol names (e.g. je_ for prefixed jemalloc) |
Custom events, markers, misc
| Flag | Purpose | |
|---|---|---|
--trace-event <EVENT> / --trace-event-pid <PID> | Attach to additional probe points | |
--trace-event-config <FILE> | JSON config defining custom events/tracks/stop triggers (see docs/TRACE_CONFIG_FORMAT.md) | |
--marker-threshold <N> | Stop after N marker instant events — requires `--continuous` | |
--marker-duration-threshold <MS> | Stop when a marker range exceeds MS ms — requires `--continuous` | |
--ringbuf-size-mib <N> | Increase BPF ring buffer size if events are lost | |
--resolve-addresses | Resolve network IPs to hostnames via DNS (off by default) |
TPU
| Flag | Purpose | |
|---|---|---|
--tpu-profile | Op-level TPU profile (same as --add-recorder tpu); requires a fixed `--duration` | |
--tpu-service-addr <HOST:PORT> | Override auto-discovery for the profiler service (port 8466) | |
--tpu-metrics | Metrics polling (same as --add-recorder tpu-metrics) | |
--tpu-metrics-addr <HOST:PORT> | Override auto-discovery for the metrics service (port 8431) | |
--tpu-metrics-interval <MS> | Metrics polling interval (default 1000 ms) |
TPU profiling
Systing can talk to the XLA/TPU runtime's gRPC services to correlate TPU activity with host-side scheduling and stacks in the same trace.
Two modes (use either or both):
- `--tpu-profile` — Full op-level profile. Connects to the XLA profiler service (port 8466), captures an XSpace profile for the trace duration, and records per-op timing, flops, and memory bytes into
tpu_op/tpu_device. Heavier; only available while a workload is actively running, and requires a fixed--duration. - `--tpu-metrics` — Lightweight polling. Connects to the RuntimeMetricService (port 8431), samples counters (duty cycle, HBM usage, latency distributions) at
--tpu-metrics-intervalintotpu_metric. Always available while the runtime is up.
Auto-discovery: By default systing scans /proc/net/tcp (across all network namespaces) for a single listener on the well-known port and connects to it, using setns if the service is in a container's netns. Zero listeners → error ("Is a TPU workload running?"); multiple listeners → disambiguate with --tpu-service-addr / --tpu-metrics-addr.
bash
# Op-level TPU profile + host scheduling for 10ssudo systing --tpu-profile -d 10 --output trace.duckdb# Lightweight metrics at 500ms alongside network & schedsudo systing --tpu-metrics --tpu-metrics-interval 500 \--add-recorder network -d 30 --output trace.duckdb# Explicit address (container / multi-device host)sudo systing --tpu-profile --tpu-service-addr 127.0.0.1:8466 -d 10 --output trace.duckdb
Output formats
- `.duckdb` — Recommended. Queryable with the
systing-analyzeCLI and MCP tools. - `.pb` / `.perfetto` — Perfetto trace, viewable at ui.perfetto.dev. This is the default if
--outputis omitted. - `.systing` / `.systing.gz` — Line-oriented profile summary (interned stacks + counts + thread metadata), no DuckDB needed. See
docs/PROFILE_EXPORT_FORMAT.md. - `--parquet-only` — Skip final output, keep raw parquet files in
--output-dir.
After capturing
Once you have a .duckdb file, use the `systing-analyze` MCP tools (if available) or the systing-analyze CLI to analyze it. See the systing-analyze skill.
Troubleshooting
- "Operation not permitted" → run with
sudo(or grantCAP_BPF+CAP_PERFMON). - Lost events / ring buffer full → increase
--ringbuf-size-mib(e.g.64). - No stack frames resolved → add
--enable-debuginfodwithDEBUGINFOD_URLSset, or install debug symbols for the target binaries. - Symbolization eating memory (CI hosts, many debug binaries) →
--symbolize-names-only, and--symbolize-elide-genericsfor heavily generic Rust/C++. - VM without hardware perf counters → add
-s/--sw-event. - `--marker-threshold` rejected → marker thresholds require
--continuous <seconds>. - "No TPU profiler/metrics service detected" → the XLA runtime isn't listening on 8466/8431. Make sure a TPU workload is running. If it's in a non-host netns systing will find it automatically; with multiple listeners, pass
--tpu-service-addr/--tpu-metrics-addr.