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initialize hwloc topology only before first fork, not always #1506

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Merged
merged 1 commit into from
Aug 29, 2025
Merged

initialize hwloc topology only before first fork, not always #1506

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15 changes: 11 additions & 4 deletions src/libumf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,13 @@ static umf_ctl_node_t CTL_NODE(umf)[] = {CTL_CHILD(provider), CTL_CHILD(pool),

void initialize_global_ctl(void) { CTL_REGISTER_MODULE(NULL, umf); }

// Benchmarks may fork multiple times and topology init is slow.
// Init topology before fork (if not already) so children don't repeat it.
// TODO: This is a hack. Better solution is needed.
#if !defined(_WIN32) && !defined(UMF_NO_HWLOC)
static void atfork_prepare(void) { umfGetTopologyReduced(); }
#endif

umf_result_t umfInit(void) {
utils_init_once(&initMutexOnce, initialize_init_mutex);

Expand Down Expand Up @@ -74,11 +81,11 @@ umf_result_t umfInit(void) {
if (TRACKER) {
LOG_DEBUG("UMF library initialized");
}
#if !defined(UMF_NO_HWLOC)
// some benchmarks uses multiple forks, and topology initialization is very slow
// so if we initialize topology before the first fork, we can get significant performance gain.
umfGetTopologyReduced();

#if !defined(_WIN32) && !defined(UMF_NO_HWLOC)
pthread_atfork(atfork_prepare, NULL, NULL);
#endif

return UMF_RESULT_SUCCESS;
}

Expand Down