[OpenMP][AIX] Affinity implementation for AIX (#84984)

This patch implements `affinity` for AIX, which is quite different from
platforms such as Linux.
- Setting CPU affinity through masks and related functions are not
supported. System call `bindprocessor()` is used to bind a thread to one
CPU per call.
- There are no system routines to get the affinity info of a thread. The
implementation of `get_system_affinity()` for AIX gets the mask of all
available CPUs, to be used as the full mask only.
- Topology is not available from the file system. It is obtained through
system SRAD (Scheduler Resource Allocation Domain).

This patch has run through the libomp LIT tests successfully with
`affinity` enabled.

(cherry picked from commit d394f3a)

openmp/runtime/src/kmp.h

@@ -818,6 +818,7 @@ class KMPAffinity {
 typedef KMPAffinity::Mask kmp_affin_mask_t;
 extern KMPAffinity *__kmp_affinity_dispatch;
 
+#ifndef KMP_OS_AIX
 class kmp_affinity_raii_t {
   kmp_affin_mask_t *mask;
   bool restored;
@@ -842,6 +843,7 @@ class kmp_affinity_raii_t {
   }
   ~kmp_affinity_raii_t() { restore(); }
 };
+#endif // !KMP_OS_AIX
 
 // Declare local char buffers with this size for printing debug and info
 // messages, using __kmp_affinity_print_mask().
@@ -3911,7 +3913,7 @@ extern void __kmp_balanced_affinity(kmp_info_t *th, int team_size);
 #if KMP_WEIGHTED_ITERATIONS_SUPPORTED
 extern int __kmp_get_first_osid_with_ecore(void);
 #endif
-#if KMP_OS_LINUX || KMP_OS_FREEBSD
+#if KMP_OS_LINUX || KMP_OS_FREEBSD || KMP_OS_AIX
 extern int kmp_set_thread_affinity_mask_initial(void);
 #endif
 static inline void __kmp_assign_root_init_mask() {

openmp/runtime/src/kmp_affinity.cpp

@@ -2906,12 +2906,17 @@ static inline const char *__kmp_cpuinfo_get_envvar() {
 }
 
 // Parse /proc/cpuinfo (or an alternate file in the same format) to obtain the
-// affinity map.
+// affinity map. On AIX, the map is obtained through system SRAD (Scheduler
+// Resource Allocation Domain).
 static bool __kmp_affinity_create_cpuinfo_map(int *line,
                                               kmp_i18n_id_t *const msg_id) {
+  *msg_id = kmp_i18n_null;
+
+#if KMP_OS_AIX
+  unsigned num_records = __kmp_xproc;
+#else
   const char *filename = __kmp_cpuinfo_get_filename();
   const char *envvar = __kmp_cpuinfo_get_envvar();
-  *msg_id = kmp_i18n_null;
 
   if (__kmp_affinity.flags.verbose) {
     KMP_INFORM(AffParseFilename, "KMP_AFFINITY", filename);
@@ -2970,6 +2975,7 @@ static bool __kmp_affinity_create_cpuinfo_map(int *line,
     *msg_id = kmp_i18n_str_CantRewindCpuinfo;
     return false;
   }
+#endif // KMP_OS_AIX
 
   // Allocate the array of records to store the proc info in.  The dummy
   // element at the end makes the logic in filling them out easier to code.
@@ -2999,6 +3005,99 @@ static bool __kmp_affinity_create_cpuinfo_map(int *line,
     INIT_PROC_INFO(threadInfo[i]);
   }
 
+#if KMP_OS_AIX
+  int smt_threads;
+  lpar_info_format1_t cpuinfo;
+  unsigned num_avail = __kmp_xproc;
+
+  if (__kmp_affinity.flags.verbose)
+    KMP_INFORM(AffParseFilename, "KMP_AFFINITY", "system info for topology");
+
+  // Get the number of SMT threads per core.
+  int retval =
+      lpar_get_info(LPAR_INFO_FORMAT1, &cpuinfo, sizeof(lpar_info_format1_t));
+  if (!retval)
+    smt_threads = cpuinfo.smt_threads;
+  else {
+    CLEANUP_THREAD_INFO;
+    *msg_id = kmp_i18n_str_UnknownTopology;
+    return false;
+  }
+
+  // Allocate a resource set containing available system resourses.
+  rsethandle_t sys_rset = rs_alloc(RS_SYSTEM);
+  if (sys_rset == NULL) {
+    CLEANUP_THREAD_INFO;
+    *msg_id = kmp_i18n_str_UnknownTopology;
+    return false;
+  }
+  // Allocate a resource set for the SRAD info.
+  rsethandle_t srad = rs_alloc(RS_EMPTY);
+  if (srad == NULL) {
+    rs_free(sys_rset);
+    CLEANUP_THREAD_INFO;
+    *msg_id = kmp_i18n_str_UnknownTopology;
+    return false;
+  }
+
+  // Get the SRAD system detail level.
+  int sradsdl = rs_getinfo(NULL, R_SRADSDL, 0);
+  if (sradsdl < 0) {
+    rs_free(sys_rset);
+    rs_free(srad);
+    CLEANUP_THREAD_INFO;
+    *msg_id = kmp_i18n_str_UnknownTopology;
+    return false;
+  }
+  // Get the number of RADs at that SRAD SDL.
+  int num_rads = rs_numrads(sys_rset, sradsdl, 0);
+  if (num_rads < 0) {
+    rs_free(sys_rset);
+    rs_free(srad);
+    CLEANUP_THREAD_INFO;
+    *msg_id = kmp_i18n_str_UnknownTopology;
+    return false;
+  }
+
+  // Get the maximum number of procs that may be contained in a resource set.
+  int max_procs = rs_getinfo(NULL, R_MAXPROCS, 0);
+  if (max_procs < 0) {
+    rs_free(sys_rset);
+    rs_free(srad);
+    CLEANUP_THREAD_INFO;
+    *msg_id = kmp_i18n_str_UnknownTopology;
+    return false;
+  }
+
+  int cur_rad = 0;
+  int num_set = 0;
+  for (int srad_idx = 0; cur_rad < num_rads && srad_idx < VMI_MAXRADS;
+       ++srad_idx) {
+    // Check if the SRAD is available in the RSET.
+    if (rs_getrad(sys_rset, srad, sradsdl, srad_idx, 0) < 0)
+      continue;
+
+    for (int cpu = 0; cpu < max_procs; cpu++) {
+      // Set the info for the cpu if it is in the SRAD.
+      if (rs_op(RS_TESTRESOURCE, srad, NULL, R_PROCS, cpu)) {
+        threadInfo[cpu][osIdIndex] = cpu;
+        threadInfo[cpu][pkgIdIndex] = cur_rad;
+        threadInfo[cpu][coreIdIndex] = cpu / smt_threads;
+        ++num_set;
+        if (num_set >= num_avail) {
+          // Done if all available CPUs have been set.
+          break;
+        }
+      }
+    }
+    ++cur_rad;
+  }
+  rs_free(sys_rset);
+  rs_free(srad);
+
+  // The topology is already sorted.
+
+#else // !KMP_OS_AIX
   unsigned num_avail = 0;
   *line = 0;
 #if KMP_ARCH_S390X
@@ -3246,6 +3345,8 @@ static bool __kmp_affinity_create_cpuinfo_map(int *line,
   qsort(threadInfo, num_avail, sizeof(*threadInfo),
         __kmp_affinity_cmp_ProcCpuInfo_phys_id);
 
+#endif // KMP_OS_AIX
+
   // The table is now sorted by pkgId / coreId / threadId, but we really don't
   // know the radix of any of the fields. pkgId's may be sparsely assigned among
   // the chips on a system. Although coreId's are usually assigned
@@ -4441,7 +4542,7 @@ static bool __kmp_aux_affinity_initialize_topology(kmp_affinity_t &affinity) {
     }
 #endif /* KMP_ARCH_X86 || KMP_ARCH_X86_64 */
 
-#if KMP_OS_LINUX
+#if KMP_OS_LINUX || KMP_OS_AIX
     if (!success) {
       int line = 0;
       success = __kmp_affinity_create_cpuinfo_map(&line, &msg_id);
@@ -4837,7 +4938,12 @@ void __kmp_affinity_uninitialize(void) {
   }
   if (__kmp_affin_origMask != NULL) {
     if (KMP_AFFINITY_CAPABLE()) {
+#if KMP_OS_AIX
+      // Uninitialize by unbinding the thread.
+      bindprocessor(BINDTHREAD, thread_self(), PROCESSOR_CLASS_ANY);
+#else
       __kmp_set_system_affinity(__kmp_affin_origMask, FALSE);
+#endif
     }
     KMP_CPU_FREE(__kmp_affin_origMask);
     __kmp_affin_origMask = NULL;
@@ -5011,7 +5117,10 @@ void __kmp_affinity_bind_init_mask(int gtid) {
     __kmp_set_system_affinity(th->th.th_affin_mask, FALSE);
   } else
 #endif
+#ifndef KMP_OS_AIX
+    // Do not set the full mask as the init mask on AIX.
     __kmp_set_system_affinity(th->th.th_affin_mask, TRUE);
+#endif
 }
 
 void __kmp_affinity_bind_place(int gtid) {
@@ -5124,15 +5233,15 @@ int __kmp_aux_set_affinity(void **mask) {
 int __kmp_aux_get_affinity(void **mask) {
   int gtid;
   int retval;
-#if KMP_OS_WINDOWS || KMP_DEBUG
+#if KMP_OS_WINDOWS || KMP_OS_AIX || KMP_DEBUG
   kmp_info_t *th;
 #endif
   if (!KMP_AFFINITY_CAPABLE()) {
     return -1;
   }
 
   gtid = __kmp_entry_gtid();
-#if KMP_OS_WINDOWS || KMP_DEBUG
+#if KMP_OS_WINDOWS || KMP_OS_AIX || KMP_DEBUG
   th = __kmp_threads[gtid];
 #else
   (void)gtid; // unused variable
@@ -5155,7 +5264,7 @@ int __kmp_aux_get_affinity(void **mask) {
     }
   }
 
-#if !KMP_OS_WINDOWS
+#if !KMP_OS_WINDOWS && !KMP_OS_AIX
 
   retval = __kmp_get_system_affinity((kmp_affin_mask_t *)(*mask), FALSE);
   KA_TRACE(
@@ -5175,7 +5284,7 @@ int __kmp_aux_get_affinity(void **mask) {
   KMP_CPU_COPY((kmp_affin_mask_t *)(*mask), th->th.th_affin_mask);
   return 0;
 
-#endif /* KMP_OS_WINDOWS */
+#endif /* !KMP_OS_WINDOWS && !KMP_OS_AIX */
 }
 
 int __kmp_aux_get_affinity_max_proc() {
@@ -5557,7 +5666,7 @@ void __kmp_balanced_affinity(kmp_info_t *th, int nthreads) {
   }
 }
 
-#if KMP_OS_LINUX || KMP_OS_FREEBSD
+#if KMP_OS_LINUX || KMP_OS_FREEBSD || KMP_OS_AIX
 // We don't need this entry for Windows because
 // there is GetProcessAffinityMask() api
 //
@@ -5592,7 +5701,11 @@ extern "C"
                 "set full mask for thread %d\n",
                 gtid));
   KMP_DEBUG_ASSERT(__kmp_affin_fullMask != NULL);
+#if KMP_OS_AIX
+  return bindprocessor(BINDTHREAD, thread_self(), PROCESSOR_CLASS_ANY);
+#else
   return __kmp_set_system_affinity(__kmp_affin_fullMask, FALSE);
+#endif
 }
 #endif
 

openmp/runtime/src/kmp_affinity.h

@@ -191,7 +191,7 @@ class KMPHwlocAffinity : public KMPAffinity {
 };
 #endif /* KMP_USE_HWLOC */
 
-#if KMP_OS_LINUX || KMP_OS_FREEBSD
+#if KMP_OS_LINUX || KMP_OS_FREEBSD || KMP_OS_AIX
 #if KMP_OS_LINUX
 /* On some of the older OS's that we build on, these constants aren't present
    in <asm/unistd.h> #included from <sys.syscall.h>. They must be the same on
@@ -314,6 +314,10 @@ class KMPHwlocAffinity : public KMPAffinity {
 #elif KMP_OS_FREEBSD
 #include <pthread.h>
 #include <pthread_np.h>
+#elif KMP_OS_AIX
+#include <sys/dr.h>
+#include <sys/rset.h>
+#define VMI_MAXRADS 64 // Maximum number of RADs allowed by AIX.
 #endif
 class KMPNativeAffinity : public KMPAffinity {
   class Mask : public KMPAffinity::Mask {
@@ -401,6 +405,70 @@ class KMPNativeAffinity : public KMPAffinity {
         ++retval;
       return retval;
     }
+#if KMP_OS_AIX
+    // On AIX, we don't have a way to get CPU(s) a thread is bound to.
+    // This routine is only used to get the full mask.
+    int get_system_affinity(bool abort_on_error) override {
+      KMP_ASSERT2(KMP_AFFINITY_CAPABLE(),
+                  "Illegal get affinity operation when not capable");
+
+      (void)abort_on_error;
+
+      // Set the mask with all CPUs that are available.
+      for (int i = 0; i < __kmp_xproc; ++i)
+        KMP_CPU_SET(i, this);
+      return 0;
+    }
+    int set_system_affinity(bool abort_on_error) const override {
+      KMP_ASSERT2(KMP_AFFINITY_CAPABLE(),
+
+                  "Illegal set affinity operation when not capable");
+
+      int location;
+      int gtid = __kmp_entry_gtid();
+      int tid = thread_self();
+
+      // Unbind the thread if it was bound to any processors before so that
+      // we can bind the thread to CPUs specified by the mask not others.
+      int retval = bindprocessor(BINDTHREAD, tid, PROCESSOR_CLASS_ANY);
+
+      // On AIX, we can only bind to one instead of a set of CPUs with the
+      // bindprocessor() system call.
+      KMP_CPU_SET_ITERATE(location, this) {
+        if (KMP_CPU_ISSET(location, this)) {
+          retval = bindprocessor(BINDTHREAD, tid, location);
+          if (retval == -1 && errno == 1) {
+            rsid_t rsid;
+            rsethandle_t rsh;
+            // Put something in rsh to prevent compiler warning
+            // about uninitalized use
+            rsh = rs_alloc(RS_EMPTY);
+            rsid.at_pid = getpid();
+            if (RS_DEFAULT_RSET != ra_getrset(R_PROCESS, rsid, 0, rsh)) {
+              retval = ra_detachrset(R_PROCESS, rsid, 0);
+              retval = bindprocessor(BINDTHREAD, tid, location);
+            }
+          }
+          if (retval == 0) {
+            KA_TRACE(10, ("__kmp_set_system_affinity:  Done binding "
+                          "T#%d to cpu=%d.\n",
+                          gtid, location));
+            continue;
+          }
+          int error = errno;
+          if (abort_on_error) {
+            __kmp_fatal(KMP_MSG(FunctionError, "bindprocessor()"),
+                        KMP_ERR(error), __kmp_msg_null);
+            KA_TRACE(10, ("__kmp_set_system_affinity:  Error binding "
+                          "T#%d to cpu=%d, errno=%d.\n",
+                          gtid, location, error));
+            return error;
+          }
+        }
+      }
+      return 0;
+    }
+#else // !KMP_OS_AIX
     int get_system_affinity(bool abort_on_error) override {
       KMP_ASSERT2(KMP_AFFINITY_CAPABLE(),
                   "Illegal get affinity operation when not capable");
@@ -443,6 +511,7 @@ class KMPNativeAffinity : public KMPAffinity {
       }
       return error;
     }
+#endif // KMP_OS_AIX
   };
   void determine_capable(const char *env_var) override {
     __kmp_affinity_determine_capable(env_var);
@@ -471,7 +540,7 @@ class KMPNativeAffinity : public KMPAffinity {
   }
   api_type get_api_type() const override { return NATIVE_OS; }
 };
-#endif /* KMP_OS_LINUX || KMP_OS_FREEBSD */
+#endif /* KMP_OS_LINUX || KMP_OS_FREEBSD || KMP_OS_AIX */
 
 #if KMP_OS_WINDOWS
 class KMPNativeAffinity : public KMPAffinity {

openmp/runtime/src/kmp_os.h

@@ -75,7 +75,8 @@
 #error Unknown compiler
 #endif
 
-#if (KMP_OS_LINUX || KMP_OS_WINDOWS || KMP_OS_FREEBSD) && !KMP_OS_WASI
+#if (KMP_OS_LINUX || KMP_OS_WINDOWS || KMP_OS_FREEBSD || KMP_OS_AIX) &&        \
+    !KMP_OS_WASI
 #define KMP_AFFINITY_SUPPORTED 1
 #if KMP_OS_WINDOWS && KMP_ARCH_X86_64
 #define KMP_GROUP_AFFINITY 1