[Openmp-commits] [PATCH] D40358: Use hyperbarrier by default on all architectures

[Jonas Hahnfeld via Phabricator via Openmp-commits]

Hahnfeld created this revision.

All architectures except x86_64 used the linear barrier implementation
by default which doesn't give good performance for a larger number
of threads.

Improvements for PARALLEL overhead (EPCC) with this patch on a Power8
system (2 sockets x 10 cores x 8 threads, OMP_PLACES=cores)

   20 threads:  4.55us -> 3.49us
   40 threads:  8.84us -> 4.06us
   80 threads: 19.18us -> 4.74us
  160 threads: 54.22us -> 6.73us


https://reviews.llvm.org/D40358

Files:
  runtime/src/kmp_global.cpp


Index: runtime/src/kmp_global.cpp
===================================================================
--- runtime/src/kmp_global.cpp
+++ runtime/src/kmp_global.cpp
@@ -76,25 +76,16 @@
 
 // Barrier method defaults, settings, and strings.
 // branch factor = 2^branch_bits (only relevant for tree & hyper barrier types)
-#if KMP_ARCH_X86_64
 kmp_uint32 __kmp_barrier_gather_bb_dflt = 2;
 /* branch_factor = 4 */ /* hyper2: C78980 */
 kmp_uint32 __kmp_barrier_release_bb_dflt = 2;
 /* branch_factor = 4 */ /* hyper2: C78980 */
-#else
-kmp_uint32 __kmp_barrier_gather_bb_dflt = 2;
-/* branch_factor = 4 */ /* communication in core for MIC */
-kmp_uint32 __kmp_barrier_release_bb_dflt = 2;
-/* branch_factor = 4 */ /* communication in core for MIC */
-#endif // KMP_ARCH_X86_64
-#if KMP_ARCH_X86_64
-kmp_bar_pat_e __kmp_barrier_gather_pat_dflt = bp_hyper_bar; /* hyper2: C78980 */
-kmp_bar_pat_e __kmp_barrier_release_pat_dflt =
-    bp_hyper_bar; /* hyper2: C78980 */
-#else
-kmp_bar_pat_e __kmp_barrier_gather_pat_dflt = bp_linear_bar;
-kmp_bar_pat_e __kmp_barrier_release_pat_dflt = bp_linear_bar;
-#endif
+
+kmp_bar_pat_e __kmp_barrier_gather_pat_dflt = bp_hyper_bar;
+/* hyper2: C78980 */
+kmp_bar_pat_e __kmp_barrier_release_pat_dflt = bp_hyper_bar;
+/* hyper2: C78980 */
+
 kmp_uint32 __kmp_barrier_gather_branch_bits[bs_last_barrier] = {0};
 kmp_uint32 __kmp_barrier_release_branch_bits[bs_last_barrier] = {0};
 kmp_bar_pat_e __kmp_barrier_gather_pattern[bs_last_barrier] = {bp_linear_bar};


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