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[OpenMP][VE] Limit the number of threads to create #66729

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Sep 20, 2023
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[OpenMP][VE] Limit the number of threads to create #66729

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7 changes: 7 additions & 0 deletions openmp/runtime/src/kmp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1153,8 +1153,15 @@ extern void __kmp_init_target_task();
#if defined(PTHREAD_THREADS_MAX) && PTHREAD_THREADS_MAX < INT_MAX
#define KMP_MAX_NTH PTHREAD_THREADS_MAX
#else
#ifdef __ve__
// VE's pthread supports only up to 64 threads per a VE process.
// Please check p. 14 of following documentation for more details.
// https://sxauroratsubasa.sakura.ne.jp/documents/veos/en/VEOS_high_level_design.pdf
#define KMP_MAX_NTH 64
#else
#define KMP_MAX_NTH INT_MAX
#endif
#endif
#endif /* KMP_MAX_NTH */

#ifdef PTHREAD_STACK_MIN
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8 changes: 8 additions & 0 deletions openmp/runtime/src/z_Linux_util.cpp
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Expand Up @@ -1894,13 +1894,21 @@ void __kmp_runtime_initialize(void) {

/* Query the maximum number of threads */
__kmp_type_convert(sysconf(_SC_THREAD_THREADS_MAX), &(__kmp_sys_max_nth));
#ifdef __ve__
if (__kmp_sys_max_nth == -1) {
// VE's pthread supports only up to 64 threads per a VE process.
// So we use that KMP_MAX_NTH (predefined as 64) here.
__kmp_sys_max_nth = KMP_MAX_NTH;
}
#else
if (__kmp_sys_max_nth == -1) {
/* Unlimited threads for NPTL */
__kmp_sys_max_nth = INT_MAX;
} else if (__kmp_sys_max_nth <= 1) {
/* Can't tell, just use PTHREAD_THREADS_MAX */
__kmp_sys_max_nth = KMP_MAX_NTH;
}
#endif

/* Query the minimum stack size */
__kmp_sys_min_stksize = sysconf(_SC_THREAD_STACK_MIN);
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