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fix(trace): emit kernel TIDs and thread-name metadata #15

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Merged
olantwin merged 1 commit into from
Jun 11, 2026
Merged

fix(trace): emit kernel TIDs and thread-name metadata #15

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27 changes: 23 additions & 4 deletions src/chrome_trace.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,12 +18,15 @@

#ifdef AEGIR_ENABLE_TRACE

#include <sys/syscall.h>
#include <unistd.h>

#include <atomic>
#include <chrono>
#include <cstdio>
#include <cstdlib>
#include <mutex>
#include <thread>
#include <string>

namespace aegir::trace {

Expand Down Expand Up @@ -64,10 +67,13 @@ inline long long now_us() {
.count();
}

// Kernel thread ID (matches what perf/ps/top show) fits in 32 bits, so the
// JSON parser in ui.perfetto.dev sees distinct values —
// std::hash<std::thread::id> produces ~10^18 numbers that JavaScript's float64
// collapses into one track.
inline long long thread_id() {
static thread_local long long id = static_cast<long long>(
std::hash<std::thread::id>{}(std::this_thread::get_id()) &
0x7fffffffffffffffLL);
static thread_local long long id =
static_cast<long long>(syscall(SYS_gettid));
return id;
}

Expand All @@ -94,6 +100,17 @@ inline void write_counter(char const* cat, char const* name, long long value) {
thread_id(), value);
}

inline void set_thread_name(std::string const& name) {
auto* f = file_handle();
if (!f) return;
std::lock_guard lock(write_mutex());
std::fprintf(f,
"%s{\"name\":\"thread_name\",\"ph\":\"M\","
"\"pid\":1,\"tid\":%lld,\"args\":{\"name\":\"%s\"}}",
first_event().exchange(false) ? "" : ",\n", thread_id(),
name.c_str());
}
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coderabbitai[bot] marked this conversation as resolved.

class ScopedEvent {
public:
ScopedEvent(char const* cat, char const* name)
Expand All @@ -119,10 +136,12 @@ class ScopedEvent {
}
#define AEGIR_TRACE_COUNTER(cat, name, value) \
::aegir::trace::write_counter(cat, name, static_cast<long long>(value))
#define AEGIR_TRACE_THREAD_NAME(name) ::aegir::trace::set_thread_name(name)

#else // !AEGIR_ENABLE_TRACE

#define AEGIR_TRACE_EVENT(cat, name) ((void)0)
#define AEGIR_TRACE_COUNTER(cat, name, value) ((void)0)
#define AEGIR_TRACE_THREAD_NAME(name) ((void)0)

#endif
2 changes: 2 additions & 0 deletions src/geant4_module.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,7 @@ class Geant4Sim {

master_thread_ = std::thread([this, &ready_promise] {
try {
AEGIR_TRACE_THREAD_NAME("g4_master");
{
AEGIR_TRACE_EVENT("g4", "init_master");
auto* rm = new G4MTRunManager();
Expand Down Expand Up @@ -214,6 +215,7 @@ class Geant4Sim {
void init_worker() {
AEGIR_TRACE_EVENT("g4", "init_worker");
int id = next_thread_id_.fetch_add(1);
AEGIR_TRACE_THREAD_NAME("g4_worker_" + std::to_string(id));
G4Threading::G4SetThreadId(id);
G4WorkerThread::BuildGeometryAndPhysicsVector();

Expand Down