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38 #if defined(HAVE_SCHED_H) && defined(HAVE_SCHED_GETAFFINITY)
41 #include <sys/syscall.h>
48 #include "types/commrec.h"
49 #include "types/hw_info.h"
50 #include "gmx_cpuid.h"
52 #include "gmx_omp_nthreads.h"
54 #include "md_logging.h"
56 #include "gmx_thread_affinity.h"
58 #include "thread_mpi/threads.h"
62 get_thread_affinity_layout(FILE *fplog,
64 const gmx_hw_info_t * hwinfo,
66 int pin_offset, int * pin_stride,
67 const int **locality_order)
69 int nhwthreads, npkg, ncores, nhwthreads_per_core, rc;
72 const int * hwthread_id;
73 gmx_bool bPickPinStride;
77 gmx_fatal(FARGS, "Negative thread pinning offset requested");
81 gmx_fatal(FARGS, "Negative thread pinning stride requested");
84 rc = gmx_cpuid_topology(hwinfo->cpuid_info, &nhwthreads, &npkg, &ncores,
86 &pkg_id, &core_id, &hwthread_id, locality_order);
90 /* topology information not available or invalid, ignore it */
91 nhwthreads = hwinfo->nthreads_hw_avail;
92 *locality_order = NULL;
96 /* We don't know anything about the hardware, don't pin */
97 md_print_warn(cr, fplog,
98 "NOTE: We don't know how many logical cores we have, will not pin threads");
104 if (nthreads > nhwthreads)
106 /* We are oversubscribing, don't pin */
107 md_print_warn(NULL, fplog,
108 "WARNING: Oversubscribing the CPU, will not pin threads");
113 if (pin_offset + nthreads > nhwthreads)
115 /* We are oversubscribing, don't pin */
116 md_print_warn(NULL, fplog,
117 "WARNING: The requested pin offset is too large for the available logical cores,\n"
118 " will not pin threads");
124 /* do we need to choose the pinning stride? */
125 bPickPinStride = (*pin_stride == 0);
129 if (rc == 0 && pin_offset + nthreads*nhwthreads_per_core <= nhwthreads)
131 /* Put one thread on each physical core */
132 *pin_stride = nhwthreads_per_core;
136 /* We don't know if we have SMT, and if we do, we don't know
137 * if hw threads in the same physical core are consecutive.
138 * Without SMT the pinning layout should not matter too much.
139 * so we assume a consecutive layout and maximally spread out"
140 * the threads at equal threads per core.
141 * Note that IBM is the major non-x86 case with cpuid support
142 * and probably threads are already pinned by the queuing system,
143 * so we wouldn't end up here in the first place.
145 *pin_stride = (nhwthreads - pin_offset)/nthreads;
150 /* Check the placement of the thread with the largest index to make sure
151 * that the offset & stride doesn't cause pinning beyond the last hardware thread. */
152 if (pin_offset + (nthreads-1)*(*pin_stride) >= nhwthreads)
154 /* We are oversubscribing, don't pin */
155 md_print_warn(NULL, fplog,
156 "WARNING: The requested pinning stride is too large for the available logical cores,\n"
157 " will not pin threads");
165 fprintf(fplog, "Pinning threads with a%s logical core stride of %d\n",
166 bPickPinStride ? "n auto-selected" : " user-specified",
173 /* Set CPU affinity. Can be important for performance.
174 On some systems (e.g. Cray) CPU Affinity is set by default.
175 But default assigning doesn't work (well) with only some ranks
176 having threads. This causes very low performance.
177 External tools have cumbersome syntax for setting affinity
178 in the case that only some ranks have threads.
179 Thus it is important that GROMACS sets the affinity internally
180 if only PME is using threads.
183 gmx_set_thread_affinity(FILE *fplog,
185 gmx_hw_opt_t *hw_opt,
186 const gmx_hw_info_t *hwinfo)
188 int nth_affinity_set, thread_id_node, thread_id,
189 nthread_local, nthread_node, nthread_hw_max, nphyscore;
191 /* these are inherently global properties that are shared among all threads
193 static const int *locality_order;
195 static gmx_bool have_locality_order = FALSE;
196 static tMPI_Thread_mutex_t locality_order_mtx =
197 TMPI_THREAD_MUTEX_INITIALIZER;
198 static tMPI_Thread_cond_t locality_order_cond =
199 TMPI_THREAD_COND_INITIALIZER;
201 if (hw_opt->thread_affinity == threadaffOFF)
207 /* If the tMPI thread affinity setting is not supported encourage the user
208 * to report it as it's either a bug or an exotic platform which we might
209 * want to support. */
210 if (tMPI_Thread_setaffinity_support() != TMPI_SETAFFINITY_SUPPORT_YES)
212 /* we know Mac OS doesn't support setting thread affinity, so there's
213 no point in warning the user in that case. In any other case
214 the user might be able to do something about it. */
216 md_print_warn(NULL, fplog,
217 "Can not set thread affinities on the current platform. On NUMA systems this\n"
218 "can cause performance degradation. If you think your platform should support\n"
219 "setting affinities, contact the GROMACS developers.");
220 #endif /* __APPLE__ */
224 /* threads on this MPI process or TMPI thread */
225 if (cr->duty & DUTY_PP)
227 nthread_local = gmx_omp_nthreads_get(emntNonbonded);
231 nthread_local = gmx_omp_nthreads_get(emntPME);
234 /* map the current process to cores */
236 nthread_node = nthread_local;
238 if (PAR(cr) || MULTISIM(cr))
240 /* We need to determine a scan of the thread counts in this
245 MPI_Comm_split(MPI_COMM_WORLD, gmx_hostname_num(), cr->rank_intranode,
247 MPI_Scan(&nthread_local, &thread_id_node, 1, MPI_INT, MPI_SUM, comm_intra);
248 /* MPI_Scan is inclusive, but here we need exclusive */
249 thread_id_node -= nthread_local;
250 /* Get the total number of threads on this physical node */
251 MPI_Allreduce(&nthread_local, &nthread_node, 1, MPI_INT, MPI_SUM, comm_intra);
252 MPI_Comm_free(&comm_intra);
256 if (hw_opt->thread_affinity == threadaffAUTO &&
257 nthread_node != hwinfo->nthreads_hw_avail)
259 if (nthread_node > 1 && nthread_node < hwinfo->nthreads_hw_avail)
261 md_print_warn(cr, fplog,
262 "NOTE: The number of threads is not equal to the number of (logical) cores\n"
263 " and the -pin option is set to auto: will not pin thread to cores.\n"
264 " This can lead to significant performance degradation.\n"
265 " Consider using -pin on (and -pinoffset in case you run multiple jobs).\n");
272 if (hw_opt->core_pinning_offset != 0)
274 offset = hw_opt->core_pinning_offset;
275 md_print_info(cr, fplog, "Applying core pinning offset %d\n", offset);
278 /* hw_opt is shared among tMPI threads, so for thread safety we need to do
279 * the layout detection only on master as core_pinning_stride is an in-out
280 * parameter and gets auto-set depending on its initial value.
282 * This is not thread-safe with multi-simulations, but that's anyway not
283 * supported by tMPI. */
289 ret = tMPI_Thread_mutex_lock(&locality_order_mtx);
292 goto locality_order_err;
294 rc = get_thread_affinity_layout(fplog, cr, hwinfo,
296 offset, &hw_opt->core_pinning_stride,
298 have_locality_order = TRUE;
299 ret = tMPI_Thread_cond_broadcast(&locality_order_cond);
302 tMPI_Thread_mutex_unlock(&locality_order_mtx);
303 goto locality_order_err;
305 ret = tMPI_Thread_mutex_unlock(&locality_order_mtx);
308 goto locality_order_err;
314 /* all other threads wait for the locality order data. */
315 ret = tMPI_Thread_mutex_lock(&locality_order_mtx);
318 goto locality_order_err;
321 while (!have_locality_order)
323 ret = tMPI_Thread_cond_wait(&locality_order_cond,
324 &locality_order_mtx);
327 tMPI_Thread_mutex_unlock(&locality_order_mtx);
328 goto locality_order_err;
331 ret = tMPI_Thread_mutex_unlock(&locality_order_mtx);
334 goto locality_order_err;
340 /* Incompatible layout, don't pin, warning was already issued */
344 /* Set the per-thread affinity. In order to be able to check the success
345 * of affinity settings, we will set nth_affinity_set to 1 on threads
346 * where the affinity setting succeded and to 0 where it failed.
347 * Reducing these 0/1 values over the threads will give the total number
348 * of threads on which we succeeded.
350 nth_affinity_set = 0;
351 #pragma omp parallel firstprivate(thread_id_node) num_threads(nthread_local) \
352 reduction(+:nth_affinity_set)
355 gmx_bool setaffinity_ret;
357 thread_id = gmx_omp_get_thread_num();
358 thread_id_node += thread_id;
359 index = offset + thread_id_node*hw_opt->core_pinning_stride;
360 if (locality_order != NULL)
362 core = locality_order[index];
369 setaffinity_ret = tMPI_Thread_setaffinity_single(tMPI_Thread_self(), core);
371 /* store the per-thread success-values of the setaffinity */
372 nth_affinity_set = (setaffinity_ret == 0);
376 fprintf(debug, "On rank %2d, thread %2d, core %2d the affinity setting returned %d\n",
377 cr->nodeid, gmx_omp_get_thread_num(), core, setaffinity_ret);
381 if (nth_affinity_set > nthread_local)
385 sprintf(msg, "Looks like we have set affinity for more threads than "
386 "we have (%d > %d)!\n", nth_affinity_set, nthread_local);
391 /* check & warn if some threads failed to set their affinities */
392 if (nth_affinity_set != nthread_local)
394 char sbuf1[STRLEN], sbuf2[STRLEN];
396 /* sbuf1 contains rank info, while sbuf2 OpenMP thread info */
397 sbuf1[0] = sbuf2[0] = '\0';
398 /* Only add rank info if we have more than one rank. */
402 #ifdef GMX_THREAD_MPI
403 sprintf(sbuf1, "In tMPI thread #%d: ", cr->nodeid);
404 #else /* GMX_LIB_MPI */
405 sprintf(sbuf1, "In MPI process #%d: ", cr->nodeid);
410 if (nthread_local > 1)
412 sprintf(sbuf2, "for %d/%d thread%s ",
413 nthread_local - nth_affinity_set, nthread_local,
414 nthread_local > 1 ? "s" : "");
417 md_print_warn(NULL, fplog,
418 "WARNING: %sAffinity setting %sfailed.\n"
419 " This can cause performance degradation! If you think your setting are\n"
420 " correct, contact the GROMACS developers.",
427 /* any error in affinity setting shouldn't be fatal, but should generate
429 md_print_warn(NULL, fplog,
430 "WARNING: Obtaining affinity information failed due to a basic system error: %s.\n"
431 " This can cause performance degradation! ",
436 /* Check the process affinity mask and if it is found to be non-zero,
437 * will honor it and disable mdrun internal affinity setting.
438 * Note that this will only work on Linux as we use a GNU feature.
441 gmx_check_thread_affinity_set(FILE *fplog, const t_commrec *cr,
442 gmx_hw_opt_t *hw_opt, int ncpus,
443 gmx_bool bAfterOpenmpInit)
445 #ifdef HAVE_SCHED_GETAFFINITY
446 cpu_set_t mask_current;
447 int i, ret, cpu_count, cpu_set;
451 if (hw_opt->thread_affinity == threadaffOFF)
453 /* internal affinity setting is off, don't bother checking process affinity */
457 CPU_ZERO(&mask_current);
458 if ((ret = sched_getaffinity(0, sizeof(cpu_set_t), &mask_current)) != 0)
460 /* failed to query affinity mask, will just return */
463 fprintf(debug, "Failed to query affinity mask (error %d)", ret);
468 /* Before proceeding with the actual check, make sure that the number of
469 * detected CPUs is >= the CPUs in the current set.
470 * We need to check for CPU_COUNT as it was added only in glibc 2.6. */
472 if (ncpus < CPU_COUNT(&mask_current))
476 fprintf(debug, "%d CPUs detected, but %d was returned by CPU_COUNT",
477 ncpus, CPU_COUNT(&mask_current));
481 #endif /* CPU_COUNT */
484 for (i = 0; (i < ncpus && i < CPU_SETSIZE); i++)
486 bAllSet = bAllSet && (CPU_ISSET(i, &mask_current) != 0);
491 if (hw_opt->thread_affinity == threadaffAUTO)
493 if (!bAfterOpenmpInit)
495 md_print_warn(cr, fplog,
496 "Non-default thread affinity set, disabling internal thread affinity");
500 md_print_warn(cr, fplog,
501 "Non-default thread affinity set probably by the OpenMP library,\n"
502 "disabling internal thread affinity");
504 hw_opt->thread_affinity = threadaffOFF;
508 /* Only warn once, at the last check (bAfterOpenmpInit==TRUE) */
509 if (bAfterOpenmpInit)
511 md_print_warn(cr, fplog,
512 "Overriding thread affinity set outside %s\n",
519 fprintf(debug, "Non-default affinity mask found\n");
526 fprintf(debug, "Default affinity mask found\n");
529 #endif /* HAVE_SCHED_GETAFFINITY */