Fix implementation of OMP_THREAD_LIMIT
This change fixes the implementation of OMP_THREAD_LIMIT. The implementation of
this previously was not restricted to a contention group (but it should be,
according to the spec), and this is fixed here. A field is added to root thread
to store a counter of the threads in the contention group. An extra check is
added when reserving threads for a parallel region that checks this variable and
compares to threadlimit-var, which is implemented as a new global variable,
kmp_cg_max_nth. Associated settings changes were also made, and clean up of
comments that referred to OMP_THREAD_LIMIT, but should refer to the new
KMP_DEVICE_THREAD_LIMIT (added in an earlier patch).
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D35912
llvm-svn: 309319
diff --git a/openmp/runtime/src/kmp_runtime.cpp b/openmp/runtime/src/kmp_runtime.cpp
index 286f4a7..bed1407 100644
--- a/openmp/runtime/src/kmp_runtime.cpp
+++ b/openmp/runtime/src/kmp_runtime.cpp
@@ -881,7 +881,7 @@
KMP_ASSERT(0);
}
- // Respect KMP_ALL_THREADS, KMP_DEVICE_THREAD_LIMIT, OMP_THREAD_LIMIT.
+ // Respect KMP_ALL_THREADS/KMP_DEVICE_THREAD_LIMIT.
if (__kmp_nth + new_nthreads -
(root->r.r_active ? 1 : root->r.r_hot_team->t.t_nproc) >
__kmp_max_nth) {
@@ -899,12 +899,41 @@
KMP_HNT(Unset_ALL_THREADS), __kmp_msg_null);
}
if (tl_nthreads == 1) {
- KC_TRACE(10, ("__kmp_reserve_threads: T#%d KMP_ALL_THREADS reduced "
- "reservation to 1 thread\n",
+ KC_TRACE(10, ("__kmp_reserve_threads: T#%d KMP_DEVICE_THREAD_LIMIT "
+ "reduced reservation to 1 thread\n",
master_tid));
return 1;
}
- KC_TRACE(10, ("__kmp_reserve_threads: T#%d KMP_ALL_THREADS reduced "
+ KC_TRACE(10, ("__kmp_reserve_threads: T#%d KMP_DEVICE_THREAD_LIMIT reduced "
+ "reservation to %d threads\n",
+ master_tid, tl_nthreads));
+ new_nthreads = tl_nthreads;
+ }
+
+ // Respect OMP_THREAD_LIMIT
+ if (root->r.r_cg_nthreads + new_nthreads -
+ (root->r.r_active ? 1 : root->r.r_hot_team->t.t_nproc) >
+ __kmp_cg_max_nth) {
+ int tl_nthreads = __kmp_cg_max_nth - root->r.r_cg_nthreads +
+ (root->r.r_active ? 1 : root->r.r_hot_team->t.t_nproc);
+ if (tl_nthreads <= 0) {
+ tl_nthreads = 1;
+ }
+
+ // If dyn-var is false, emit a 1-time warning.
+ if (!get__dynamic_2(parent_team, master_tid) && (!__kmp_reserve_warn)) {
+ __kmp_reserve_warn = 1;
+ __kmp_msg(kmp_ms_warning,
+ KMP_MSG(CantFormThrTeam, set_nthreads, tl_nthreads),
+ KMP_HNT(Unset_ALL_THREADS), __kmp_msg_null);
+ }
+ if (tl_nthreads == 1) {
+ KC_TRACE(10, ("__kmp_reserve_threads: T#%d OMP_THREAD_LIMIT "
+ "reduced reservation to 1 thread\n",
+ master_tid));
+ return 1;
+ }
+ KC_TRACE(10, ("__kmp_reserve_threads: T#%d OMP_THREAD_LIMIT reduced "
"reservation to %d threads\n",
master_tid, tl_nthreads));
new_nthreads = tl_nthreads;
@@ -3116,6 +3145,7 @@
root->r.r_in_parallel = 0;
root->r.r_blocktime = __kmp_dflt_blocktime;
root->r.r_nested = __kmp_dflt_nested;
+ root->r.r_cg_nthreads = 1;
/* setup the root team for this task */
/* allocate the root team structure */
@@ -3508,7 +3538,7 @@
// Note that __kmp_threads_capacity is not bounded by __kmp_max_nth. If
// __kmp_max_nth is set to some value less than __kmp_sys_max_nth by the
- // user via OMP_THREAD_LIMIT, then __kmp_threads_capacity may become
+ // user via KMP_DEVICE_THREAD_LIMIT, then __kmp_threads_capacity may become
// > __kmp_max_nth in one of two ways:
//
// 1) The initialization thread (gtid = 0) exits. __kmp_threads[0]
@@ -3889,6 +3919,8 @@
TCW_4(__kmp_nth,
__kmp_nth - 1); // __kmp_reap_thread will decrement __kmp_all_nth.
+ root->r.r_cg_nthreads--;
+
__kmp_reap_thread(root->r.r_uber_thread, 1);
// We canot put root thread to __kmp_thread_pool, so we have to reap it istead
@@ -4169,6 +4201,7 @@
KMP_DEBUG_ASSERT(new_thr->th.th_serial_team);
TCW_4(__kmp_nth, __kmp_nth + 1);
+ root->r.r_cg_nthreads++;
new_thr->th.th_task_state = 0;
new_thr->th.th_task_state_top = 0;
@@ -4316,6 +4349,8 @@
__kmp_all_nth++;
__kmp_nth++;
+ root->r.r_cg_nthreads++;
+
// if __kmp_adjust_gtid_mode is set, then we use method #1 (sp search) for low
// numbers of procs, and method #2 (keyed API call) for higher numbers.
if (__kmp_adjust_gtid_mode) {
@@ -5378,6 +5413,7 @@
void __kmp_free_thread(kmp_info_t *this_th) {
int gtid;
kmp_info_t **scan;
+ kmp_root_t *root = this_th->th.th_root;
KA_TRACE(20, ("__kmp_free_thread: T#%d putting T#%d back on free pool.\n",
__kmp_get_gtid(), this_th->th.th_info.ds.ds_gtid));
@@ -5436,6 +5472,7 @@
__kmp_thread_pool_nth++;
TCW_4(__kmp_nth, __kmp_nth - 1);
+ root->r.r_cg_nthreads--;
#ifdef KMP_ADJUST_BLOCKTIME
/* Adjust blocktime back to user setting or default if necessary */
@@ -6375,6 +6412,7 @@
__kmp_dflt_team_nth_ub = __kmp_sys_max_nth;
}
__kmp_max_nth = __kmp_sys_max_nth;
+ __kmp_cg_max_nth = __kmp_sys_max_nth;
// Three vars below moved here from __kmp_env_initialize() "KMP_BLOCKTIME"
// part
@@ -6977,7 +7015,7 @@
if (num_teams * num_threads > __kmp_max_nth) {
int new_threads = __kmp_max_nth / num_teams;
if (!__kmp_reserve_warn) { // user asked for too many threads
- __kmp_reserve_warn = 1; // that conflicts with OMP_THREAD_LIMIT
+ __kmp_reserve_warn = 1; // that conflicts with KMP_DEVICE_THREAD_LIMIT
__kmp_msg(kmp_ms_warning,
KMP_MSG(CantFormThrTeam, num_threads, new_threads),
KMP_HNT(Unset_ALL_THREADS), __kmp_msg_null);