[Openmp-commits] [openmp] r309319 - Fix implementation of OMP_THREAD_LIMIT
Jonathan Peyton via Openmp-commits
openmp-commits at lists.llvm.org
Thu Jul 27 13:58:41 PDT 2017
Author: jlpeyton
Date: Thu Jul 27 13:58:41 2017
New Revision: 309319
URL: http://llvm.org/viewvc/llvm-project?rev=309319&view=rev
Log:
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
Added:
openmp/trunk/runtime/test/env/omp_thread_limit.c
Modified:
openmp/trunk/runtime/src/i18n/en_US.txt
openmp/trunk/runtime/src/kmp.h
openmp/trunk/runtime/src/kmp_ftn_entry.h
openmp/trunk/runtime/src/kmp_global.cpp
openmp/trunk/runtime/src/kmp_runtime.cpp
openmp/trunk/runtime/src/kmp_settings.cpp
Modified: openmp/trunk/runtime/src/i18n/en_US.txt
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/src/i18n/en_US.txt?rev=309319&r1=309318&r2=309319&view=diff
==============================================================================
--- openmp/trunk/runtime/src/i18n/en_US.txt (original)
+++ openmp/trunk/runtime/src/i18n/en_US.txt Thu Jul 27 13:58:41 2017
@@ -433,7 +433,7 @@ SubmitBugReport "Please sub
OBSOLETE "Check NLSPATH environment variable, its value is \"%1$s\"."
ChangeStackLimit "Please try changing the shell stack limit or adjusting the "
"OMP_STACKSIZE environment variable."
-Unset_ALL_THREADS "Consider unsetting KMP_ALL_THREADS and OMP_THREAD_LIMIT (if either is set)."
+Unset_ALL_THREADS "Consider unsetting KMP_DEVICE_THREAD_LIMIT (KMP_ALL_THREADS) and OMP_THREAD_LIMIT (if either is set)."
Set_ALL_THREADPRIVATE "Consider setting KMP_ALL_THREADPRIVATE to a value larger than %1$d."
PossibleSystemLimitOnThreads "This could also be due to a system-related limit on the number of threads."
DuplicateLibrary "This means that multiple copies of the OpenMP runtime have been "
Modified: openmp/trunk/runtime/src/kmp.h
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/src/kmp.h?rev=309319&r1=309318&r2=309319&view=diff
==============================================================================
--- openmp/trunk/runtime/src/kmp.h (original)
+++ openmp/trunk/runtime/src/kmp.h Thu Jul 27 13:58:41 2017
@@ -2689,6 +2689,7 @@ typedef struct kmp_base_root {
kmp_lock_t r_begin_lock;
volatile int r_begin;
int r_blocktime; /* blocktime for this root and descendants */
+ int r_cg_nthreads; // count of active threads in a contention group
} kmp_base_root_t;
typedef union KMP_ALIGN_CACHE kmp_root {
@@ -2863,8 +2864,10 @@ extern int __kmp_xproc; /* number of pro
extern int __kmp_avail_proc; /* number of processors available to the process */
extern size_t __kmp_sys_min_stksize; /* system-defined minimum stack size */
extern int __kmp_sys_max_nth; /* system-imposed maximum number of threads */
-extern int
- __kmp_max_nth; /* maximum total number of concurrently-existing threads */
+// maximum total number of concurrently-existing threads on device
+extern int __kmp_max_nth;
+// maximum total number of concurrently-existing threads in a contention group
+extern int __kmp_cg_max_nth;
extern int __kmp_threads_capacity; /* capacity of the arrays __kmp_threads and
__kmp_root */
extern int __kmp_dflt_team_nth; /* default number of threads in a parallel
Modified: openmp/trunk/runtime/src/kmp_ftn_entry.h
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/src/kmp_ftn_entry.h?rev=309319&r1=309318&r2=309319&view=diff
==============================================================================
--- openmp/trunk/runtime/src/kmp_ftn_entry.h (original)
+++ openmp/trunk/runtime/src/kmp_ftn_entry.h Thu Jul 27 13:58:41 2017
@@ -550,7 +550,7 @@ int FTN_STDCALL xexpand(FTN_GET_THREAD_L
__kmp_serial_initialize();
};
/* global ICV */
- return __kmp_max_nth;
+ return __kmp_cg_max_nth;
#endif
}
Modified: openmp/trunk/runtime/src/kmp_global.cpp
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/src/kmp_global.cpp?rev=309319&r1=309318&r2=309319&view=diff
==============================================================================
--- openmp/trunk/runtime/src/kmp_global.cpp (original)
+++ openmp/trunk/runtime/src/kmp_global.cpp Thu Jul 27 13:58:41 2017
@@ -135,6 +135,7 @@ int __kmp_avail_proc = 0;
size_t __kmp_sys_min_stksize = KMP_MIN_STKSIZE;
int __kmp_sys_max_nth = KMP_MAX_NTH;
int __kmp_max_nth = 0;
+int __kmp_cg_max_nth = 0;
int __kmp_threads_capacity = 0;
int __kmp_dflt_team_nth = 0;
int __kmp_dflt_team_nth_ub = 0;
Modified: openmp/trunk/runtime/src/kmp_runtime.cpp
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/src/kmp_runtime.cpp?rev=309319&r1=309318&r2=309319&view=diff
==============================================================================
--- openmp/trunk/runtime/src/kmp_runtime.cpp (original)
+++ openmp/trunk/runtime/src/kmp_runtime.cpp Thu Jul 27 13:58:41 2017
@@ -881,7 +881,7 @@ static int __kmp_reserve_threads(kmp_roo
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 @@ static int __kmp_reserve_threads(kmp_roo
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 @@ static void __kmp_initialize_root(kmp_ro
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 @@ static int __kmp_expand_threads(int nWis
// 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 @@ static int __kmp_reset_root(int gtid, km
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_info_t *__kmp_allocate_thread(kmp_ro
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_info_t *__kmp_allocate_thread(kmp_ro
__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 @@ kmp_team_t *__kmp_reap_team(kmp_team_t *
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 @@ void __kmp_free_thread(kmp_info_t *this_
__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 @@ static void __kmp_do_serial_initialize(v
__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 @@ void __kmp_push_num_teams(ident_t *id, i
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);
Modified: openmp/trunk/runtime/src/kmp_settings.cpp
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/src/kmp_settings.cpp?rev=309319&r1=309318&r2=309319&view=diff
==============================================================================
--- openmp/trunk/runtime/src/kmp_settings.cpp (original)
+++ openmp/trunk/runtime/src/kmp_settings.cpp Thu Jul 27 13:58:41 2017
@@ -569,7 +569,7 @@ static void __kmp_stg_print_size(kmp_str
// Parse and print functions.
// -----------------------------------------------------------------------------
-// KMP_ALL_THREADS, KMP_DEVICE_THREAD_LIMIT, OMP_THREAD_LIMIT
+// KMP_DEVICE_THREAD_LIMIT, KMP_ALL_THREADS
static void __kmp_stg_parse_device_thread_limit(char const *name,
char const *value, void *data) {
@@ -599,6 +599,20 @@ static void __kmp_stg_print_device_threa
} // __kmp_stg_print_device_thread_limit
// -----------------------------------------------------------------------------
+// OMP_THREAD_LIMIT
+static void __kmp_stg_parse_thread_limit(char const *name, char const *value,
+ void *data) {
+ __kmp_stg_parse_int(name, value, 1, __kmp_sys_max_nth, &__kmp_cg_max_nth);
+ K_DIAG(1, ("__kmp_cg_max_nth == %d\n", __kmp_cg_max_nth));
+
+} // __kmp_stg_parse_thread_limit
+
+static void __kmp_stg_print_thread_limit(kmp_str_buf_t *buffer,
+ char const *name, void *data) {
+ __kmp_stg_print_int(buffer, name, __kmp_cg_max_nth);
+} // __kmp_stg_print_thread_limit
+
+// -----------------------------------------------------------------------------
// KMP_BLOCKTIME
static void __kmp_stg_parse_blocktime(char const *name, char const *value,
@@ -4386,8 +4400,8 @@ static kmp_setting_t __kmp_stg_table[] =
{"KMP_TASKLOOP_MIN_TASKS", __kmp_stg_parse_taskloop_min_tasks,
__kmp_stg_print_taskloop_min_tasks, NULL, 0, 0},
#endif
- {"OMP_THREAD_LIMIT", __kmp_stg_parse_device_thread_limit,
- __kmp_stg_print_device_thread_limit, NULL, 0, 0},
+ {"OMP_THREAD_LIMIT", __kmp_stg_parse_thread_limit,
+ __kmp_stg_print_thread_limit, NULL, 0, 0},
{"OMP_WAIT_POLICY", __kmp_stg_parse_wait_policy,
__kmp_stg_print_wait_policy, NULL, 0, 0},
{"KMP_DISP_NUM_BUFFERS", __kmp_stg_parse_disp_buffers,
@@ -4687,27 +4701,22 @@ static void __kmp_stg_init(void) {
}; // if
}
- { // Initialize KMP_DEVICE_THREAD_LIMIT, KMP_ALL_THREADS, and
- // OMP_THREAD_LIMIT data.
+ { // Initialize KMP_DEVICE_THREAD_LIMIT and KMP_ALL_THREADS
kmp_setting_t *kmp_device_thread_limit =
__kmp_stg_find("KMP_DEVICE_THREAD_LIMIT"); // 1st priority.
kmp_setting_t *kmp_all_threads =
__kmp_stg_find("KMP_ALL_THREADS"); // 2nd priority.
- kmp_setting_t *omp_thread_limit =
- __kmp_stg_find("OMP_THREAD_LIMIT"); // 3rd priority.
// !!! volatile keyword is Intel (R) C Compiler bug CQ49908 workaround.
- static kmp_setting_t *volatile rivals[4];
+ static kmp_setting_t *volatile rivals[3];
int i = 0;
rivals[i++] = kmp_device_thread_limit;
rivals[i++] = kmp_all_threads;
- rivals[i++] = omp_thread_limit;
rivals[i++] = NULL;
kmp_device_thread_limit->data = CCAST(kmp_setting_t **, rivals);
kmp_all_threads->data = CCAST(kmp_setting_t **, rivals);
- omp_thread_limit->data = CCAST(kmp_setting_t **, rivals);
}
#if KMP_AFFINITY_SUPPORTED
Added: openmp/trunk/runtime/test/env/omp_thread_limit.c
URL: http://llvm.org/viewvc/llvm-project/openmp/trunk/runtime/test/env/omp_thread_limit.c?rev=309319&view=auto
==============================================================================
--- openmp/trunk/runtime/test/env/omp_thread_limit.c (added)
+++ openmp/trunk/runtime/test/env/omp_thread_limit.c Thu Jul 27 13:58:41 2017
@@ -0,0 +1,82 @@
+// RUN: %libomp-compile && env OMP_THREAD_LIMIT=4 %libomp-run 4
+// RUN: %libomp-compile && env OMP_THREAD_LIMIT=7 %libomp-run 7
+//
+// OMP_THREAD_LIMIT=N should imply that no more than N threads are active in
+// a contention group
+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+#include "omp_testsuite.h"
+
+int failed = 0;
+
+void usage() {
+ fprintf(stderr, "usage: omp_thread_limit <n>\n");
+}
+
+void verify(const char* file_name, int line_number, int team_size) {
+ int num_threads = omp_get_num_threads();
+ if (team_size != num_threads) {
+#pragma omp critical(A)
+ {
+ char label[256];
+ snprintf(label, sizeof(label), "%s:%d", file_name, line_number);
+ failed = 1;
+ printf("failed: %s: team_size(%d) != omp_get_num_threads(%d)\n",
+ label, team_size, num_threads);
+ }
+ }
+}
+
+int main(int argc, char** argv)
+{
+ int cl_thread_limit;
+
+ if (argc != 2) {
+ usage();
+ return 1;
+ }
+ cl_thread_limit = atoi(argv[1]);
+
+ omp_set_dynamic(0);
+ if (omp_get_thread_limit() != cl_thread_limit) {
+ fprintf(stderr, "omp_get_thread_limit failed with %d, should be%d\n",
+ omp_get_thread_limit(), cl_thread_limit);
+ return 1;
+ }
+ else if (omp_get_max_threads() > cl_thread_limit) {
+#if _OPENMP
+ int team_size = cl_thread_limit;
+#else
+ int team_size = 1;
+#endif
+ omp_set_num_threads(19);
+ verify(__FILE__, __LINE__, 1);
+#pragma omp parallel
+ {
+ verify(__FILE__, __LINE__, team_size);
+ verify(__FILE__, __LINE__, team_size);
+ }
+ verify(__FILE__, __LINE__, 1);
+
+ omp_set_nested(1);
+#pragma omp parallel num_threads(3)
+ {
+ verify(__FILE__, __LINE__, 3);
+#pragma omp master
+#pragma omp parallel num_threads(21)
+ {
+ verify(__FILE__, __LINE__, team_size-2);
+ verify(__FILE__, __LINE__, team_size-2);
+ }
+ }
+ verify(__FILE__, __LINE__, 1);
+
+ return failed;
+ } else {
+ fprintf(stderr, "This test is not applicable for max num_threads='%d'\n",
+ omp_get_max_threads());
+ return 0;
+ }
+
+}
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