[OpenMP] Add skewed iteration distribution in static-steal schedule for hybrid systems

[jlpeyton]

Summary

This commit adds skewed distribution of iterations in dynamic
schedule (static steal) for hybrid systems when thread affinity is assigned.
Currently, it distributes the iterations at 60:40 ratio. Consider this loop with
dynamic schedule type, for (int i = 0; i < 100; ++i)

In a hybrid system with 20 processes (16 CORE and 4 ATOM core), 88 iterations
will be assigned to performance cores and 12 iterations will be assigned to
efficient cores. Each thread with CORE core will process 5
iterations + extras and with ATOM core will process 3 iterations.

[jlpeyton]

Base on https://reviews.llvm.org/D156727 so topology information is consistent and fix accidental use of ds_gtid instead of ds_tid.

[jdoerfert]

can we have a test for this?

openmp/runtime/src/kmp_dispatch.cpp

96

floats are not double precision

154

Probably easier to read if the non weighted case was handled first.

548

Is it really helping that we use a macro to elide the code? It makes the impl more complex for sure.

[jlpeyton]

If its better to move this to GitHub, I can do that. Sorry, I had forgotten about this.

Test case still requires to be run on x86 with hybrid architecture (e.g., Alder Lake machine), but is now enabled.

I've compartmentalized the macro-guarded code for better readability, it's hard to remove the guard completely since the code relies on x86-specific guards (e.g., use of KMP_HW_CORE_TYPE_ATOM).

openmp/runtime/src/kmp.h

/* This fix replaces gettimeofday with clock_gettime for better scalability on
    the Altix.  Requires user code to be linked with -lrt. */
 //#define FIX_SGI_CLOCK
 
 /* Defines for OpenMP 3.0 tasking and auto scheduling */
 
 #ifndef KMP_STATIC_STEAL_ENABLED
 #define KMP_STATIC_STEAL_ENABLED 1
 #endif
+#define KMP_WEIGHTED_ITERATIONS_SUPPORTED                                      \
+  (KMP_AFFINITY_SUPPORTED && KMP_STATIC_STEAL_ENABLED &&                       \
+   (KMP_ARCH_X86 || KMP_ARCH_X86_64))
 
 #define TASK_CURRENT_NOT_QUEUED 0
 #define TASK_CURRENT_QUEUED 1
 
 #ifdef BUILD_TIED_TASK_STACK
 #define TASK_STACK_EMPTY 0 // entries when the stack is empty
 #define TASK_STACK_BLOCK_BITS 5 // Used in TASK_STACK_SIZE and TASK_STACK_MASK
 // Number of entries in each task stack array
typedef struct kmp_affinity_flags_t {
   unsigned core_types_gran : 1;
   unsigned core_effs_gran : 1;
   unsigned omp_places : 1;
   unsigned reserved : 22;
 } kmp_affinity_flags_t;
 KMP_BUILD_ASSERT(sizeof(kmp_affinity_flags_t) == 4);
 
 typedef struct kmp_affinity_ids_t {
+  int os_id;
   int ids[KMP_HW_LAST];
-  int operator[](size_t idx) const { return ids[idx]; }
-  int &operator[](size_t idx) { return ids[idx]; }
-  kmp_affinity_ids_t &operator=(const kmp_affinity_ids_t &rhs) {
-    for (int i = 0; i < KMP_HW_LAST; ++i)
-      ids[i] = rhs[i];
-    return *this;
-  }
 } kmp_affinity_ids_t;
 
 typedef struct kmp_affinity_attrs_t {
   int core_type : 8;
   int core_eff : 8;
   unsigned valid : 1;
   unsigned reserved : 15;
 } kmp_affinity_attrs_t;

 extern kmp_affinity_t *__kmp_affinities[2];
 
 extern void __kmp_affinity_bind_thread(int which);
 
 extern kmp_affin_mask_t *__kmp_affin_fullMask;
 extern kmp_affin_mask_t *__kmp_affin_origMask;
 extern char *__kmp_cpuinfo_file;
 
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+extern int __kmp_first_osid_with_ecore;
+#endif
+
 #endif /* KMP_AFFINITY_SUPPORTED */
 
 // This needs to be kept in sync with the values in omp.h !!!
 typedef enum kmp_proc_bind_t {
   proc_bind_false = 0,
   proc_bind_true,
   proc_bind_primary,
   proc_bind_close,
typedef struct kmp_hier_private_bdata_t {
   kmp_uint64 wait_val[2];
 } kmp_hier_private_bdata_t;
 #endif
 
 typedef struct kmp_sched_flags {
   unsigned ordered : 1;
   unsigned nomerge : 1;
   unsigned contains_last : 1;
-#if KMP_USE_HIER_SCHED
-  unsigned use_hier : 1;
-  unsigned unused : 28;
-#else
-  unsigned unused : 29;
-#endif
+  unsigned use_hier : 1; // Used in KMP_USE_HIER_SCHED code
+  unsigned use_hybrid : 1; // Used in KMP_WEIGHTED_ITERATIONS_SUPPORTED code
+  unsigned unused : 27;
 } kmp_sched_flags_t;
 
 KMP_BUILD_ASSERT(sizeof(kmp_sched_flags_t) == 4);
 
 #if KMP_STATIC_STEAL_ENABLED
 typedef struct KMP_ALIGN_CACHE dispatch_private_info32 {
   kmp_int32 count;
   kmp_int32 ub;
   /* Adding KMP_ALIGN_CACHE here doesn't help / can hurt performance */
   kmp_int32 lb;
   kmp_int32 st;
   kmp_int32 tc;
   kmp_lock_t *steal_lock; // lock used for chunk stealing
+
+  kmp_uint32 ordered_lower;
+  kmp_uint32 ordered_upper;
+
   // KMP_ALIGN(32) ensures (if the KMP_ALIGN macro is turned on)
   //    a) parm3 is properly aligned and
   //    b) all parm1-4 are on the same cache line.
   // Because of parm1-4 are used together, performance seems to be better
   // if they are on the same cache line (not measured though).
 
-  struct KMP_ALIGN(32) { // AC: changed 16 to 32 in order to simplify template
-    kmp_int32 parm1; //     structures in kmp_dispatch.cpp. This should
-    kmp_int32 parm2; //     make no real change at least while padding is off.
+  struct KMP_ALIGN(32) {
+    kmp_int32 parm1;
+    kmp_int32 parm2;
     kmp_int32 parm3;
     kmp_int32 parm4;
   };
 
-  kmp_uint32 ordered_lower;
-  kmp_uint32 ordered_upper;
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+  kmp_uint32 pchunks;
+  kmp_uint32 num_procs_with_pcore;
+  kmp_int32 first_thread_with_ecore;
+#endif
 #if KMP_OS_WINDOWS
   kmp_int32 last_upper;
 #endif /* KMP_OS_WINDOWS */
 } dispatch_private_info32_t;
 
+#if CACHE_LINE <= 128
+KMP_BUILD_ASSERT(sizeof(dispatch_private_info32_t) <= 128);
+#endif
+
 typedef struct KMP_ALIGN_CACHE dispatch_private_info64 {
   kmp_int64 count; // current chunk number for static & static-steal scheduling
   kmp_int64 ub; /* upper-bound */
   /* Adding KMP_ALIGN_CACHE here doesn't help / can hurt performance */
   kmp_int64 lb; /* lower-bound */
   kmp_int64 st; /* stride */
   kmp_int64 tc; /* trip count (number of iterations) */
   kmp_lock_t *steal_lock; // lock used for chunk stealing
+
+  kmp_uint64 ordered_lower;
+  kmp_uint64 ordered_upper;
   /* parm[1-4] are used in different ways by different scheduling algorithms */
 
-  // KMP_ALIGN( 32 ) ensures ( if the KMP_ALIGN macro is turned on )
+  // KMP_ALIGN(32) ensures ( if the KMP_ALIGN macro is turned on )
   //    a) parm3 is properly aligned and
   //    b) all parm1-4 are in the same cache line.
   // Because of parm1-4 are used together, performance seems to be better
   // if they are in the same line (not measured though).
-
   struct KMP_ALIGN(32) {
     kmp_int64 parm1;
     kmp_int64 parm2;
     kmp_int64 parm3;
     kmp_int64 parm4;
   };
 
-  kmp_uint64 ordered_lower;
-  kmp_uint64 ordered_upper;
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+  kmp_uint64 pchunks;
+  kmp_uint64 num_procs_with_pcore;
+  kmp_int64 first_thread_with_ecore;
+#endif
+
 #if KMP_OS_WINDOWS
   kmp_int64 last_upper;
 #endif /* KMP_OS_WINDOWS */
 } dispatch_private_info64_t;
+
+#if CACHE_LINE <= 128
+KMP_BUILD_ASSERT(sizeof(dispatch_private_info64_t) <= 128);
+#endif
+
 #else /* KMP_STATIC_STEAL_ENABLED */
 typedef struct KMP_ALIGN_CACHE dispatch_private_info32 {
   kmp_int32 lb;
   kmp_int32 ub;
   kmp_int32 st;
   kmp_int32 tc;
 
   kmp_int32 parm1;

 extern void __kmp_affinity_determine_capable(const char *env_var);
 extern int __kmp_aux_set_affinity(void **mask);
 extern int __kmp_aux_get_affinity(void **mask);
 extern int __kmp_aux_get_affinity_max_proc();
 extern int __kmp_aux_set_affinity_mask_proc(int proc, void **mask);
 extern int __kmp_aux_unset_affinity_mask_proc(int proc, void **mask);
 extern int __kmp_aux_get_affinity_mask_proc(int proc, void **mask);
 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
 extern int kmp_set_thread_affinity_mask_initial(void);
 #endif
 static inline void __kmp_assign_root_init_mask() {
   int gtid = __kmp_entry_gtid();
   kmp_root_t *r = __kmp_threads[gtid]->th.th_root;
   if (r->r.r_uber_thread == __kmp_threads[gtid] && !r->r.r_affinity_assigned) {
     __kmp_affinity_set_init_mask(gtid, /*isa_root=*/TRUE);

openmp/runtime/src/kmp_affinity.cpp

 static void __kmp_affinity_get_mask_topology_info(const kmp_affin_mask_t *mask,
                                                   kmp_affinity_ids_t &ids,
                                                   kmp_affinity_attrs_t &attrs) {
   if (!KMP_AFFINITY_CAPABLE())
     return;
 
   // Initiailze ids and attrs thread data
   for (int i = 0; i < KMP_HW_LAST; ++i)
-    ids[i] = kmp_hw_thread_t::UNKNOWN_ID;
+    ids.ids[i] = kmp_hw_thread_t::UNKNOWN_ID;
   attrs = KMP_AFFINITY_ATTRS_UNKNOWN;
 
   // Iterate through each os id within the mask and determine
   // the topology id and attribute information
   int cpu;
   int depth = __kmp_topology->get_depth();
   KMP_CPU_SET_ITERATE(cpu, mask) {
     int osid_idx = __kmp_osid_to_hwthread_map[cpu];
+    ids.os_id = cpu;
     const kmp_hw_thread_t &hw_thread = __kmp_topology->at(osid_idx);
     for (int level = 0; level < depth; ++level) {
       kmp_hw_t type = __kmp_topology->get_type(level);
       int id = hw_thread.sub_ids[level];
-      if (ids[type] == kmp_hw_thread_t::UNKNOWN_ID || ids[type] == id) {
-        ids[type] = id;
+      if (ids.ids[type] == kmp_hw_thread_t::UNKNOWN_ID || ids.ids[type] == id) {
+        ids.ids[type] = id;
       } else {
         // This mask spans across multiple topology units, set it as such
         // and mark every level below as such as well.
-        ids[type] = kmp_hw_thread_t::MULTIPLE_ID;
+        ids.ids[type] = kmp_hw_thread_t::MULTIPLE_ID;
         for (; level < depth; ++level) {
           kmp_hw_t type = __kmp_topology->get_type(level);
-          ids[type] = kmp_hw_thread_t::MULTIPLE_ID;
+          ids.ids[type] = kmp_hw_thread_t::MULTIPLE_ID;
         }
       }
     }
     if (!attrs.valid) {
       attrs.core_type = hw_thread.attrs.get_core_type();
       attrs.core_eff = hw_thread.attrs.get_core_eff();
       attrs.valid = 1;
     } else {

 }
 
 // Called when __kmp_topology is ready
 static void __kmp_aux_affinity_initialize_other_data(kmp_affinity_t &affinity) {
   // Initialize other data structures which depend on the topology
   if (__kmp_topology && __kmp_topology->get_num_hw_threads()) {
     machine_hierarchy.init(__kmp_topology->get_num_hw_threads());
     __kmp_affinity_get_topology_info(affinity);
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+    __kmp_first_osid_with_ecore = __kmp_get_first_osid_with_ecore();
+#endif
   }
 }
 
 // Create a one element mask array (set of places) which only contains the
 // initial process's affinity mask
 static void __kmp_create_affinity_none_places(kmp_affinity_t &affinity) {
   KMP_ASSERT(__kmp_affin_fullMask != NULL);
   KMP_ASSERT(affinity.type == affinity_none);

 // This function initializes the per-thread data concerning affinity including
 // the mask and topology information
 void __kmp_affinity_set_init_mask(int gtid, int isa_root) {
 
   kmp_info_t *th = (kmp_info_t *)TCR_SYNC_PTR(__kmp_threads[gtid]);
 
   // Set the thread topology information to default of unknown
   for (int id = 0; id < KMP_HW_LAST; ++id)
-    th->th.th_topology_ids[id] = kmp_hw_thread_t::UNKNOWN_ID;
+    th->th.th_topology_ids.ids[id] = kmp_hw_thread_t::UNKNOWN_ID;
   th->th.th_topology_attrs = KMP_AFFINITY_ATTRS_UNKNOWN;
 
   if (!KMP_AFFINITY_CAPABLE()) {
     return;
   }
 
   if (th->th.th_affin_mask == NULL) {
     KMP_CPU_ALLOC(th->th.th_affin_mask);
int __kmp_aux_get_affinity_mask_proc(int proc, void **mask) {
   }
   if (!KMP_CPU_ISSET(proc, __kmp_affin_fullMask)) {
     return 0;
   }
 
   return KMP_CPU_ISSET(proc, (kmp_affin_mask_t *)(*mask));
 }
 
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+// Returns first os proc id with ATOM core
+int __kmp_get_first_osid_with_ecore(void) {
+  int low = 0;
+  int high = __kmp_topology->get_num_hw_threads() - 1;
+  int mid = 0;
+  while (high - low > 1) {
+    mid = (high + low) / 2;
+    if (__kmp_topology->at(mid).attrs.get_core_type() ==
+        KMP_HW_CORE_TYPE_CORE) {
+      low = mid + 1;
+    } else {
+      high = mid;
+    }
+  }
+  if (__kmp_topology->at(mid).attrs.get_core_type() == KMP_HW_CORE_TYPE_ATOM) {
+    return mid;
+  }
+  return -1;
+}
+#endif
+
 // Dynamic affinity settings - Affinity balanced
 void __kmp_balanced_affinity(kmp_info_t *th, int nthreads) {
   KMP_DEBUG_ASSERT(th);
   bool fine_gran = true;
   int tid = th->th.th_info.ds.ds_tid;
   const char *env_var = "KMP_AFFINITY";
 
   // Do not perform balanced affinity for the hidden helper threads

openmp/runtime/src/kmp_dispatch.h

template <typename T> struct dispatch_private_infoXX_template {
   typedef typename traits_t<T>::signed_t ST;
   UT count; // unsigned
   T ub;
   /* Adding KMP_ALIGN_CACHE here doesn't help / can hurt performance */
   T lb;
   ST st; // signed
   UT tc; // unsigned
   kmp_lock_t *steal_lock; // lock used for chunk stealing
+
+  UT ordered_lower; // unsigned
+  UT ordered_upper; // unsigned
+
   /* parm[1-4] are used in different ways by different scheduling algorithms */
 
-  // KMP_ALIGN( 32 ) ensures ( if the KMP_ALIGN macro is turned on )
+  // KMP_ALIGN(32) ensures ( if the KMP_ALIGN macro is turned on )
   //    a) parm3 is properly aligned and
   //    b) all parm1-4 are in the same cache line.
   // Because of parm1-4 are used together, performance seems to be better
   // if they are in the same line (not measured though).
-
   struct KMP_ALIGN(32) { // compiler does not accept sizeof(T)*4
     T parm1;
     T parm2;
     T parm3;
     T parm4;
   };
 
-  UT ordered_lower; // unsigned
-  UT ordered_upper; // unsigned
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+  UT pchunks; // total number of chunks for processes with p-core
+  UT num_procs_with_pcore; // number of threads with p-core
+  T first_thread_with_ecore;
+#endif
 #if KMP_OS_WINDOWS
   T last_upper;
 #endif /* KMP_OS_WINDOWS */
 };
 
 #else /* KMP_STATIC_STEAL_ENABLED */
 
 // replaces dispatch_private_info{32,64} structures and

openmp/runtime/src/kmp_dispatch.cpp

static inline int __kmp_get_monotonicity(ident_t *loc, enum sched_type schedule,
   else if (SCHEDULE_HAS_NONMONOTONIC(schedule))
     monotonicity = SCHEDULE_NONMONOTONIC;
   else if (SCHEDULE_HAS_MONOTONIC(schedule))
     monotonicity = SCHEDULE_MONOTONIC;
 
   return monotonicity;
 }
 
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+// Return floating point number rounded to two decimal points
+static inline float __kmp_round_2decimal_val(float num) {
+  return (float)(static_cast<int>(num * 100 + 0.5)) / 100;
+}
+static inline int __kmp_get_round_val(float num) {
+  return static_cast<int>(num < 0 ? num - 0.5 : num + 0.5);
+}
+#endif
+
+template <typename T>
+inline void
+__kmp_initialize_self_buffer(kmp_team_t *team, T id,
+                             dispatch_private_info_template<T> *pr,
+                             typename traits_t<T>::unsigned_t nchunks, T nproc,
+                             typename traits_t<T>::unsigned_t &init,
+                             T &small_chunk, T &extras, T &p_extra) {
+
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+  if (pr->flags.use_hybrid) {
+    kmp_info_t *th = __kmp_threads[__kmp_gtid_from_tid((int)id, team)];
+    kmp_hw_core_type_t type =
+        (kmp_hw_core_type_t)th->th.th_topology_attrs.core_type;
+    T pchunks = pr->u.p.pchunks;
+    T echunks = nchunks - pchunks;
+    T num_procs_with_pcore = pr->u.p.num_procs_with_pcore;
+    T num_procs_with_ecore = nproc - num_procs_with_pcore;
+    T first_thread_with_ecore = pr->u.p.first_thread_with_ecore;
+    T big_chunk =
+        pchunks / num_procs_with_pcore; // chunks per thread with p-core
+    small_chunk =
+        echunks / num_procs_with_ecore; // chunks per thread with e-core
+
+    extras =
+        (pchunks % num_procs_with_pcore) + (echunks % num_procs_with_ecore);
+
+    p_extra = (big_chunk - small_chunk);
+
+    if (type == KMP_HW_CORE_TYPE_CORE) {
+      if (id < first_thread_with_ecore) {
+        init = id * small_chunk + id * p_extra + (id < extras ? id : extras);
+      } else {
+        init = id * small_chunk + (id - num_procs_with_ecore) * p_extra +
+               (id < extras ? id : extras);
+      }
+    } else {
+      if (id == first_thread_with_ecore) {
+        init = id * small_chunk + id * p_extra + (id < extras ? id : extras);
+      } else {
+        init = id * small_chunk + first_thread_with_ecore * p_extra +
+               (id < extras ? id : extras);
+      }
+    }
+    p_extra = (type == KMP_HW_CORE_TYPE_CORE) ? p_extra : 0;
+    return;
+  }
+#endif
+
+  small_chunk = nchunks / nproc; // chunks per thread
+  extras = nchunks % nproc;
+  p_extra = 0;
+  init = id * small_chunk + (id < extras ? id : extras);
+}
+
 #if KMP_STATIC_STEAL_ENABLED
 enum { // values for steal_flag (possible states of private per-loop buffer)
   UNUSED = 0,
   CLAIMED = 1, // owner thread started initialization
   READY = 2, // available for stealing
   THIEF = 3 // finished by owner, or claimed by thief
   // possible state changes:
   // 0 -> 1 owner only, sync
if (pr->flags.ordered) {
       pr->u.p.ordered_lower = 1;
       pr->u.p.ordered_upper = 0;
     }
   }
 
   switch (schedule) {
 #if KMP_STATIC_STEAL_ENABLED
   case kmp_sch_static_steal: {
-    T ntc, init;
+    T ntc, init = 0;
 
     KD_TRACE(100,
              ("__kmp_dispatch_init_algorithm: T#%d kmp_sch_static_steal case\n",
               gtid));
 
     ntc = (tc % chunk ? 1 : 0) + tc / chunk;
     if (nproc > 1 && ntc >= nproc) {
       KMP_COUNT_BLOCK(OMP_LOOP_STATIC_STEAL);
       T id = tid;
-      T small_chunk, extras;
+      T small_chunk, extras, p_extra = 0;
       kmp_uint32 old = UNUSED;
       int claimed = pr->steal_flag.compare_exchange_strong(old, CLAIMED);
       if (traits_t<T>::type_size > 4) {
         // AC: TODO: check if 16-byte CAS available and use it to
         // improve performance (probably wait for explicit request
         // before spending time on this).
         // For now use dynamically allocated per-private-buffer lock,
         // free memory in __kmp_dispatch_next when status==0.
         pr->u.p.steal_lock = (kmp_lock_t *)__kmp_allocate(sizeof(kmp_lock_t));
         __kmp_init_lock(pr->u.p.steal_lock);
       }
+
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+      // Iterations are divided in a 60/40 skewed distribution among CORE and
+      // ATOM processors for hybrid systems
+      bool use_hybrid = false;
+      kmp_hw_core_type_t core_type = KMP_HW_CORE_TYPE_UNKNOWN;
+      T first_thread_with_ecore = 0;
+      T num_procs_with_pcore = 0;
+      T num_procs_with_ecore = 0;
+      T p_ntc = 0, e_ntc = 0;
+      if (__kmp_is_hybrid_cpu() && __kmp_affinity.type != affinity_none &&
+          __kmp_affinity.type != affinity_explicit) {
+        use_hybrid = true;
+        core_type = (kmp_hw_core_type_t)th->th.th_topology_attrs.core_type;
+        if (core_type != KMP_HW_CORE_TYPE_UNKNOWN &&
+            __kmp_first_osid_with_ecore > -1) {
+          for (int i = 0; i < team->t.t_nproc; ++i) {
+            kmp_hw_core_type_t type = (kmp_hw_core_type_t)team->t.t_threads[i]
+                                          ->th.th_topology_attrs.core_type;
+            int id = team->t.t_threads[i]->th.th_topology_ids.os_id;
+            if (id == __kmp_first_osid_with_ecore) {
+              first_thread_with_ecore =
+                  team->t.t_threads[i]->th.th_info.ds.ds_tid;
+            }
+            if (type == KMP_HW_CORE_TYPE_CORE) {
+              num_procs_with_pcore++;
+            } else if (type == KMP_HW_CORE_TYPE_ATOM) {
+              num_procs_with_ecore++;
+            } else {
+              use_hybrid = false;
+              break;
+            }
+          }
+        }
+        if (num_procs_with_pcore > 0 && num_procs_with_ecore > 0) {
+          float multiplier = 60.0 / 40.0;
+          float p_ratio = (float)num_procs_with_pcore / nproc;
+          float e_ratio = (float)num_procs_with_ecore / nproc;
+          float e_multiplier =
+              (float)1 /
+              (((multiplier * num_procs_with_pcore) / nproc) + e_ratio);
+          float p_multiplier = multiplier * e_multiplier;
+          p_ntc = __kmp_get_round_val(ntc * p_ratio * p_multiplier);
+          if ((int)p_ntc > (int)(ntc * p_ratio * p_multiplier))
+            e_ntc =
+                (int)(__kmp_round_2decimal_val(ntc * e_ratio * e_multiplier));
+          else
+            e_ntc = __kmp_get_round_val(ntc * e_ratio * e_multiplier);
+          KMP_DEBUG_ASSERT(ntc == p_ntc + e_ntc);
+
+          // Use regular static steal if not enough chunks for skewed
+          // distribution
+          use_hybrid = (use_hybrid && (p_ntc >= num_procs_with_pcore &&
+                                       e_ntc >= num_procs_with_ecore)
+                            ? true
+                            : false);
+        } else {
+          use_hybrid = false;
+        }
+      }
+      pr->flags.use_hybrid = use_hybrid;
+      pr->u.p.pchunks = p_ntc;
+      pr->u.p.num_procs_with_pcore = num_procs_with_pcore;
+      pr->u.p.first_thread_with_ecore = first_thread_with_ecore;
+
+      if (use_hybrid) {
+        KMP_DEBUG_ASSERT(nproc == num_procs_with_pcore + num_procs_with_ecore);
+        T big_chunk = p_ntc / num_procs_with_pcore;
+        small_chunk = e_ntc / num_procs_with_ecore;
+
+        extras =
+            (p_ntc % num_procs_with_pcore) + (e_ntc % num_procs_with_ecore);
+
+        p_extra = (big_chunk - small_chunk);
+
+        if (core_type == KMP_HW_CORE_TYPE_CORE) {
+          if (id < first_thread_with_ecore) {
+            init =
+                id * small_chunk + id * p_extra + (id < extras ? id : extras);
+          } else {
+            init = id * small_chunk + (id - num_procs_with_ecore) * p_extra +
+                   (id < extras ? id : extras);
+          }
+        } else {
+          if (id == first_thread_with_ecore) {
+            init =
+                id * small_chunk + id * p_extra + (id < extras ? id : extras);
+          } else {
+            init = id * small_chunk + first_thread_with_ecore * p_extra +
+                   (id < extras ? id : extras);
+          }
+        }
+        p_extra = (core_type == KMP_HW_CORE_TYPE_CORE) ? p_extra : 0;
+      } else
+#endif
+      {
         small_chunk = ntc / nproc;
         extras = ntc % nproc;
-
         init = id * small_chunk + (id < extras ? id : extras);
+        p_extra = 0;
+      }
       pr->u.p.count = init;
       if (claimed) { // are we succeeded in claiming own buffer?
-        pr->u.p.ub = init + small_chunk + (id < extras ? 1 : 0);
+        pr->u.p.ub = init + small_chunk + p_extra + (id < extras ? 1 : 0);
         // Other threads will inspect steal_flag when searching for a victim.
         // READY means other threads may steal from this thread from now on.
         KMP_ATOMIC_ST_REL(&pr->steal_flag, READY);
       } else {
         // other thread has stolen whole our range
         KMP_DEBUG_ASSERT(pr->steal_flag == THIEF);
         pr->u.p.ub = init; // mark there is no iterations to work on
       }
if (traits_t<T>::type_size > 4) {
           }
           if (KMP_ATOMIC_LD_RLX(&v->steal_flag) == UNUSED) {
             kmp_uint32 old = UNUSED;
             // try to steal whole range from inactive victim
             status = v->steal_flag.compare_exchange_strong(old, THIEF);
             if (status) {
               // initialize self buffer with victim's whole range of chunks
               T id = victimId;
-              T small_chunk, extras;
-              small_chunk = nchunks / nproc; // chunks per thread
-              extras = nchunks % nproc;
-              init = id * small_chunk + (id < extras ? id : extras);
+              T small_chunk = 0, extras = 0, p_extra = 0;
+              __kmp_initialize_self_buffer<T>(team, id, pr, nchunks, nproc,
+                                              init, small_chunk, extras,
+                                              p_extra);
               __kmp_acquire_lock(lck, gtid);
               pr->u.p.count = init + 1; // exclude one we execute immediately
-              pr->u.p.ub = init + small_chunk + (id < extras ? 1 : 0);
+              pr->u.p.ub = init + small_chunk + p_extra + (id < extras ? 1 : 0);
               __kmp_release_lock(lck, gtid);
               pr->u.p.parm4 = (id + 1) % nproc; // remember neighbour tid
               // no need to reinitialize other thread invariants: lb, st, etc.
 #ifdef KMP_DEBUG
               {
                 char *buff;
                 // create format specifiers before the debug output
-                buff = __kmp_str_format(
-                    "__kmp_dispatch_next: T#%%d stolen chunks from T#%%d, "
+                buff = __kmp_str_format("__kmp_dispatch_next_algorithm: T#%%d "
+                                        "stolen chunks from T#%%d, "
                                         "count:%%%s ub:%%%s\n",
                                         traits_t<UT>::spec, traits_t<T>::spec);
                 KD_TRACE(10, (buff, gtid, id, pr->u.p.count, pr->u.p.ub));
                 __kmp_str_free(&buff);
               }
 #endif
               // activate non-empty buffer and let others steal from us
               if (pr->u.p.count < (UT)pr->u.p.ub)
                 KMP_ATOMIC_ST_REL(&pr->steal_flag, READY);
               break;
#endif
           }
           if (KMP_ATOMIC_LD_RLX(&v->steal_flag) == UNUSED) {
             kmp_uint32 old = UNUSED;
             // try to steal whole range from inactive victim
             status = v->steal_flag.compare_exchange_strong(old, THIEF);
             if (status) {
               // initialize self buffer with victim's whole range of chunks
               T id = victimId;
-              T small_chunk, extras;
-              small_chunk = nchunks / nproc; // chunks per thread
-              extras = nchunks % nproc;
-              init = id * small_chunk + (id < extras ? id : extras);
+              T small_chunk = 0, extras = 0, p_extra = 0;
+              __kmp_initialize_self_buffer<T>(team, id, pr, nchunks, nproc,
+                                              init, small_chunk, extras,
+                                              p_extra);
               vnew.p.count = init + 1;
-              vnew.p.ub = init + small_chunk + (id < extras ? 1 : 0);
+              vnew.p.ub = init + small_chunk + p_extra + (id < extras ? 1 : 0);
               // write pair (count, ub) at once atomically
 #if KMP_ARCH_X86
               KMP_XCHG_FIXED64((volatile kmp_int64 *)(&pr->u.p.count), vnew.b);
 #else
               *(volatile kmp_int64 *)(&pr->u.p.count) = vnew.b;
 #endif
               pr->u.p.parm4 = (id + 1) % nproc; // remember neighbour tid
               // no need to initialize other thread invariants: lb, st, etc.
 #ifdef KMP_DEBUG
               {
                 char *buff;
                 // create format specifiers before the debug output
-                buff = __kmp_str_format(
-                    "__kmp_dispatch_next: T#%%d stolen chunks from T#%%d, "
+                buff = __kmp_str_format("__kmp_dispatch_next_algorithm: T#%%d "
+                                        "stolen chunks from T#%%d, "
                                         "count:%%%s ub:%%%s\n",
                                         traits_t<UT>::spec, traits_t<T>::spec);
                 KD_TRACE(10, (buff, gtid, id, pr->u.p.count, pr->u.p.ub));
                 __kmp_str_free(&buff);
               }
 #endif
               // activate non-empty buffer and let others steal from us
               if (pr->u.p.count < (UT)pr->u.p.ub)
                 KMP_ATOMIC_ST_REL(&pr->steal_flag, READY);
               break;

openmp/runtime/src/kmp_global.cpp

 // Regular thread affinity settings from KMP_AFFINITY
 kmp_affinity_t __kmp_affinity = KMP_AFFINITY_INIT("KMP_AFFINITY");
 // Hidden helper thread affinity settings from KMP_HIDDEN_HELPER_AFFINITY
 kmp_affinity_t __kmp_hh_affinity =
     KMP_AFFINITY_INIT("KMP_HIDDEN_HELPER_AFFINITY");
 kmp_affinity_t *__kmp_affinities[] = {&__kmp_affinity, &__kmp_hh_affinity};
 
 char *__kmp_cpuinfo_file = NULL;
+#if KMP_WEIGHTED_ITERATIONS_SUPPORTED
+int __kmp_first_osid_with_ecore = -1;
+#endif
 
 #endif /* KMP_AFFINITY_SUPPORTED */
 
 kmp_nested_proc_bind_t __kmp_nested_proc_bind = {NULL, 0, 0};
 kmp_proc_bind_t __kmp_teams_proc_bind = proc_bind_spread;
 int __kmp_affinity_num_places = 0;
 int __kmp_display_affinity = FALSE;
 char *__kmp_affinity_format = NULL;

openmp/runtime/test/worksharing/for/omp_for_schedule_dynamic.c

 // RUN: %libomp-compile-and-run
+// RUN: env KMP_AFFINITY=compact,0 %libomp-run
 /*
  * Test for dynamic scheduling with chunk size
  * Method: calculate how many times the iteration space is dispatched
  *     and judge if each dispatch has the requested chunk size
  *     unless it is the last one.
  * It is possible for two adjacent chunks are assigned to the same thread
  * Modified by Chunhua Liao
  */