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37 #include "gromacs/legacyheaders/gmx_thread_affinity.h"
46 #ifdef HAVE_SCHED_AFFINITY
48 # include <sys/syscall.h>
51 #include "thread_mpi/threads.h"
53 #include "gromacs/legacyheaders/copyrite.h"
54 #include "gromacs/legacyheaders/gmx_cpuid.h"
55 #include "gromacs/legacyheaders/gmx_omp_nthreads.h"
56 #include "gromacs/legacyheaders/md_logging.h"
57 #include "gromacs/legacyheaders/typedefs.h"
58 #include "gromacs/legacyheaders/types/commrec.h"
59 #include "gromacs/legacyheaders/types/hw_info.h"
60 #include "gromacs/utility/basenetwork.h"
61 #include "gromacs/utility/cstringutil.h"
62 #include "gromacs/utility/fatalerror.h"
63 #include "gromacs/utility/gmxomp.h"
64 #include "gromacs/utility/smalloc.h"
67 get_thread_affinity_layout(FILE *fplog,
69 const gmx_hw_info_t * hwinfo,
71 int pin_offset, int * pin_stride,
72 const int **locality_order)
74 int nhwthreads, npkg, ncores, nhwthreads_per_core, rc;
77 const int * hwthread_id;
78 gmx_bool bPickPinStride;
82 gmx_fatal(FARGS, "Negative thread pinning offset requested");
86 gmx_fatal(FARGS, "Negative thread pinning stride requested");
89 rc = gmx_cpuid_topology(hwinfo->cpuid_info, &nhwthreads, &npkg, &ncores,
91 &pkg_id, &core_id, &hwthread_id, locality_order);
95 /* topology information not available or invalid, ignore it */
96 nhwthreads = hwinfo->nthreads_hw_avail;
97 *locality_order = NULL;
101 /* We don't know anything about the hardware, don't pin */
102 md_print_warn(cr, fplog,
103 "NOTE: We don't know how many logical cores we have, will not pin threads");
109 if (nthreads > nhwthreads)
111 /* We are oversubscribing, don't pin */
112 md_print_warn(NULL, fplog,
113 "WARNING: Oversubscribing the CPU, will not pin threads");
118 if (pin_offset + nthreads > nhwthreads)
120 /* We are oversubscribing, don't pin */
121 md_print_warn(NULL, fplog,
122 "WARNING: The requested pin offset is too large for the available logical cores,\n"
123 " will not pin threads");
129 /* do we need to choose the pinning stride? */
130 bPickPinStride = (*pin_stride == 0);
134 if (rc == 0 && pin_offset + nthreads*nhwthreads_per_core <= nhwthreads)
136 /* Put one thread on each physical core */
137 *pin_stride = nhwthreads_per_core;
141 /* We don't know if we have SMT, and if we do, we don't know
142 * if hw threads in the same physical core are consecutive.
143 * Without SMT the pinning layout should not matter too much.
144 * so we assume a consecutive layout and maximally spread out"
145 * the threads at equal threads per core.
146 * Note that IBM is the major non-x86 case with cpuid support
147 * and probably threads are already pinned by the queuing system,
148 * so we wouldn't end up here in the first place.
150 *pin_stride = (nhwthreads - pin_offset)/nthreads;
155 /* Check the placement of the thread with the largest index to make sure
156 * that the offset & stride doesn't cause pinning beyond the last hardware thread. */
157 if (pin_offset + (nthreads-1)*(*pin_stride) >= nhwthreads)
159 /* We are oversubscribing, don't pin */
160 md_print_warn(NULL, fplog,
161 "WARNING: The requested pinning stride is too large for the available logical cores,\n"
162 " will not pin threads");
170 fprintf(fplog, "Pinning threads with a%s logical core stride of %d\n",
171 bPickPinStride ? "n auto-selected" : " user-specified",
178 /* Set CPU affinity. Can be important for performance.
179 On some systems (e.g. Cray) CPU Affinity is set by default.
180 But default assigning doesn't work (well) with only some ranks
181 having threads. This causes very low performance.
182 External tools have cumbersome syntax for setting affinity
183 in the case that only some ranks have threads.
184 Thus it is important that GROMACS sets the affinity internally
185 if only PME is using threads.
188 gmx_set_thread_affinity(FILE *fplog,
190 gmx_hw_opt_t *hw_opt,
191 const gmx_hw_info_t *hwinfo)
193 int nth_affinity_set, thread0_id_node,
194 nthread_local, nthread_node, nthread_hw_max, nphyscore;
196 const int *locality_order;
199 if (hw_opt->thread_affinity == threadaffOFF)
205 /* If the tMPI thread affinity setting is not supported encourage the user
206 * to report it as it's either a bug or an exotic platform which we might
207 * want to support. */
208 if (tMPI_Thread_setaffinity_support() != TMPI_SETAFFINITY_SUPPORT_YES)
210 /* we know Mac OS doesn't support setting thread affinity, so there's
211 no point in warning the user in that case. In any other case
212 the user might be able to do something about it. */
214 md_print_warn(NULL, fplog,
215 "Can not set thread affinities on the current platform. On NUMA systems this\n"
216 "can cause performance degradation. If you think your platform should support\n"
217 "setting affinities, contact the GROMACS developers.");
218 #endif /* __APPLE__ */
222 /* threads on this MPI process or TMPI thread */
223 if (cr->duty & DUTY_PP)
225 nthread_local = gmx_omp_nthreads_get(emntNonbonded);
229 nthread_local = gmx_omp_nthreads_get(emntPME);
232 /* map the current process to cores */
234 nthread_node = nthread_local;
236 if (PAR(cr) || MULTISIM(cr))
238 /* We need to determine a scan of the thread counts in this
243 MPI_Comm_split(MPI_COMM_WORLD,
244 gmx_physicalnode_id_hash(), cr->rank_intranode,
246 MPI_Scan(&nthread_local, &thread0_id_node, 1, MPI_INT, MPI_SUM, comm_intra);
247 /* MPI_Scan is inclusive, but here we need exclusive */
248 thread0_id_node -= nthread_local;
249 /* Get the total number of threads on this physical node */
250 MPI_Allreduce(&nthread_local, &nthread_node, 1, MPI_INT, MPI_SUM, comm_intra);
251 MPI_Comm_free(&comm_intra);
255 if (hw_opt->thread_affinity == threadaffAUTO &&
256 nthread_node != hwinfo->nthreads_hw_avail)
258 if (nthread_node > 1 && nthread_node < hwinfo->nthreads_hw_avail)
260 md_print_warn(cr, fplog,
261 "NOTE: The number of threads is not equal to the number of (logical) cores\n"
262 " and the -pin option is set to auto: will not pin thread to cores.\n"
263 " This can lead to significant performance degradation.\n"
264 " Consider using -pin on (and -pinoffset in case you run multiple jobs).\n");
271 if (hw_opt->core_pinning_offset != 0)
273 offset = hw_opt->core_pinning_offset;
274 md_print_info(cr, fplog, "Applying core pinning offset %d\n", offset);
277 rc = get_thread_affinity_layout(fplog, cr, hwinfo,
279 offset, &hw_opt->core_pinning_stride,
284 /* Incompatible layout, don't pin, warning was already issued */
288 /* Set the per-thread affinity. In order to be able to check the success
289 * of affinity settings, we will set nth_affinity_set to 1 on threads
290 * where the affinity setting succeded and to 0 where it failed.
291 * Reducing these 0/1 values over the threads will give the total number
292 * of threads on which we succeeded.
294 nth_affinity_set = 0;
295 #pragma omp parallel num_threads(nthread_local) reduction(+:nth_affinity_set)
297 int thread_id, thread_id_node;
299 gmx_bool setaffinity_ret;
301 thread_id = gmx_omp_get_thread_num();
302 thread_id_node = thread0_id_node + thread_id;
303 index = offset + thread_id_node*hw_opt->core_pinning_stride;
304 if (locality_order != NULL)
306 core = locality_order[index];
313 setaffinity_ret = tMPI_Thread_setaffinity_single(tMPI_Thread_self(), core);
315 /* store the per-thread success-values of the setaffinity */
316 nth_affinity_set = (setaffinity_ret == 0);
320 fprintf(debug, "On rank %2d, thread %2d, index %2d, core %2d the affinity setting returned %d\n",
321 cr->nodeid, gmx_omp_get_thread_num(), index, core, setaffinity_ret);
325 if (nth_affinity_set > nthread_local)
329 sprintf(msg, "Looks like we have set affinity for more threads than "
330 "we have (%d > %d)!\n", nth_affinity_set, nthread_local);
335 /* check & warn if some threads failed to set their affinities */
336 if (nth_affinity_set != nthread_local)
338 char sbuf1[STRLEN], sbuf2[STRLEN];
340 /* sbuf1 contains rank info, while sbuf2 OpenMP thread info */
341 sbuf1[0] = sbuf2[0] = '\0';
342 /* Only add rank info if we have more than one rank. */
346 #ifdef GMX_THREAD_MPI
347 sprintf(sbuf1, "In tMPI thread #%d: ", cr->nodeid);
348 #else /* GMX_LIB_MPI */
349 sprintf(sbuf1, "In MPI process #%d: ", cr->nodeid);
354 if (nthread_local > 1)
356 sprintf(sbuf2, "for %d/%d thread%s ",
357 nthread_local - nth_affinity_set, nthread_local,
358 nthread_local > 1 ? "s" : "");
361 md_print_warn(NULL, fplog,
362 "WARNING: %sAffinity setting %sfailed.\n"
363 " This can cause performance degradation! If you think your setting are\n"
364 " correct, contact the GROMACS developers.",
371 /* Check the process affinity mask and if it is found to be non-zero,
372 * will honor it and disable mdrun internal affinity setting.
373 * Note that this will only work on Linux as we use a GNU feature.
376 gmx_check_thread_affinity_set(FILE *fplog,
378 gmx_hw_opt_t *hw_opt,
379 int gmx_unused nthreads_hw_avail,
380 gmx_bool bAfterOpenmpInit)
382 #ifdef HAVE_SCHED_AFFINITY
383 cpu_set_t mask_current;
384 int i, ret, cpu_count, cpu_set;
389 if (!bAfterOpenmpInit)
391 /* Check for externally set OpenMP affinity and turn off internal
392 * pinning if any is found. We need to do this check early to tell
393 * thread-MPI whether it should do pinning when spawning threads.
394 * TODO: the above no longer holds, we should move these checks later
396 if (hw_opt->thread_affinity != threadaffOFF)
399 if (!gmx_omp_check_thread_affinity(&message))
401 /* TODO: with -pin auto we should only warn when using all cores */
402 md_print_warn(cr, fplog, "%s", message);
404 hw_opt->thread_affinity = threadaffOFF;
408 /* With thread-MPI this is needed as pinning might get turned off,
409 * which needs to be known before starting thread-MPI.
410 * With thread-MPI hw_opt is processed here on the master rank
411 * and passed to the other ranks later, so we only do this on master.
417 #ifndef GMX_THREAD_MPI
422 #ifdef HAVE_SCHED_GETAFFINITY
423 if (hw_opt->thread_affinity == threadaffOFF)
425 /* internal affinity setting is off, don't bother checking process affinity */
429 CPU_ZERO(&mask_current);
430 if ((ret = sched_getaffinity(0, sizeof(cpu_set_t), &mask_current)) != 0)
432 /* failed to query affinity mask, will just return */
435 fprintf(debug, "Failed to query affinity mask (error %d)", ret);
440 /* Before proceeding with the actual check, make sure that the number of
441 * detected CPUs is >= the CPUs in the current set.
442 * We need to check for CPU_COUNT as it was added only in glibc 2.6. */
444 if (nthreads_hw_avail < CPU_COUNT(&mask_current))
448 fprintf(debug, "%d hardware threads detected, but %d was returned by CPU_COUNT",
449 nthreads_hw_avail, CPU_COUNT(&mask_current));
453 #endif /* CPU_COUNT */
456 for (i = 0; (i < nthreads_hw_avail && i < CPU_SETSIZE); i++)
458 bAllSet = bAllSet && (CPU_ISSET(i, &mask_current) != 0);
463 if (hw_opt->thread_affinity == threadaffAUTO)
465 if (!bAfterOpenmpInit)
467 md_print_warn(cr, fplog,
468 "Non-default thread affinity set, disabling internal thread affinity");
472 md_print_warn(cr, fplog,
473 "Non-default thread affinity set probably by the OpenMP library,\n"
474 "disabling internal thread affinity");
476 hw_opt->thread_affinity = threadaffOFF;
480 /* Only warn once, at the last check (bAfterOpenmpInit==TRUE) */
481 if (bAfterOpenmpInit)
483 md_print_warn(cr, fplog,
484 "Overriding thread affinity set outside %s\n",
491 fprintf(debug, "Non-default affinity mask found\n");
498 fprintf(debug, "Default affinity mask found\n");
501 #endif /* HAVE_SCHED_AFFINITY */