[Openmp-commits] [PATCH] D96749: [OpenMP] Limit number of dispatch buffers

[Jonathan Peyton via Phabricator via Openmp-commits]

jlpeyton created this revision.
jlpeyton added reviewers: AndreyChurbanov, tlwilmar, hbae, Nawrin.
jlpeyton added a project: OpenMP.
Herald added subscribers: guansong, yaxunl.
jlpeyton requested review of this revision.
Herald added a reviewer: jdoerfert.
Herald added a subscriber: sstefan1.

This patch limits the number of dispatch buffers (used for loop worksharing construct) to between 1 and 4096.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D96749

Files:
  openmp/runtime/src/kmp.h
  openmp/runtime/src/kmp_csupport.cpp
  openmp/runtime/src/kmp_ftn_entry.h
  openmp/runtime/src/kmp_settings.cpp
  openmp/runtime/test/env/kmp_dispatch_buf_range.c


Index: openmp/runtime/test/env/kmp_dispatch_buf_range.c
===================================================================
--- /dev/null
+++ openmp/runtime/test/env/kmp_dispatch_buf_range.c
@@ -0,0 +1,18 @@
+// RUN: %libomp-compile
+// RUN: env KMP_DISP_NUM_BUFFERS=0 %libomp-run 2>&1 | FileCheck --check-prefix=SMALL %s
+// RUN: env KMP_DISP_NUM_BUFFERS=4097 %libomp-run 2>&1 | FileCheck --check-prefix=LARGE %s
+// SMALL: OMP: Warning
+// SMALL-SAME: KMP_DISP_NUM_BUFFERS
+// SMALL-SAME: too small
+// LARGE: OMP: Warning
+// LARGE-SAME: KMP_DISP_NUM_BUFFERS
+// LARGE-SAME: too large
+#include <stdio.h>
+#include <stdlib.h>
+
+int main() {
+  int i;
+  #pragma omp parallel for
+  for (i = 0; i < 1000; i++) {}
+  return EXIT_SUCCESS;
+}
Index: openmp/runtime/src/kmp_settings.cpp
===================================================================
--- openmp/runtime/src/kmp_settings.cpp
+++ openmp/runtime/src/kmp_settings.cpp
@@ -1389,7 +1389,8 @@
     KMP_WARNING(EnvSerialWarn, name);
     return;
   } // read value before serial initialization only
-  __kmp_stg_parse_int(name, value, 1, KMP_MAX_NTH, &__kmp_dispatch_num_buffers);
+  __kmp_stg_parse_int(name, value, KMP_MIN_DISP_NUM_BUFF, KMP_MAX_DISP_NUM_BUFF,
+                      &__kmp_dispatch_num_buffers);
 } // __kmp_stg_parse_disp_buffers
 
 static void __kmp_stg_print_disp_buffers(kmp_str_buf_t *buffer,
Index: openmp/runtime/src/kmp_ftn_entry.h
===================================================================
--- openmp/runtime/src/kmp_ftn_entry.h
+++ openmp/runtime/src/kmp_ftn_entry.h
@@ -202,8 +202,11 @@
 #else
   // ignore after initialization because some teams have already
   // allocated dispatch buffers
-  if (__kmp_init_serial == 0 && (KMP_DEREF arg) > 0)
-    __kmp_dispatch_num_buffers = KMP_DEREF arg;
+  int num_buffers = KMP_DEREF arg;
+  if (__kmp_init_serial == FALSE && num_buffers >= KMP_MIN_DISP_NUM_BUFF &&
+      num_buffers <= KMP_MAX_DISP_NUM_BUFF) {
+    __kmp_dispatch_num_buffers = num_buffers;
+  }
 #endif
 }
 
Index: openmp/runtime/src/kmp_csupport.cpp
===================================================================
--- openmp/runtime/src/kmp_csupport.cpp
+++ openmp/runtime/src/kmp_csupport.cpp
@@ -1961,8 +1961,10 @@
 void kmpc_set_disp_num_buffers(int arg) {
   // ignore after initialization because some teams have already
   // allocated dispatch buffers
-  if (__kmp_init_serial == 0 && arg > 0)
+  if (__kmp_init_serial == FALSE && arg >= KMP_MIN_DISP_NUM_BUFF &&
+      arg <= KMP_MAX_DISP_NUM_BUFF) {
     __kmp_dispatch_num_buffers = arg;
+  }
 }
 
 int kmpc_set_affinity_mask_proc(int proc, void **mask) {
Index: openmp/runtime/src/kmp.h
===================================================================
--- openmp/runtime/src/kmp.h
+++ openmp/runtime/src/kmp.h
@@ -1126,7 +1126,10 @@
 #define KMP_MAX_CHUNK (INT_MAX - 1)
 #define KMP_DEFAULT_CHUNK 1
 
+#define KMP_MIN_DISP_NUM_BUFF 1
 #define KMP_DFLT_DISP_NUM_BUFF 7
+#define KMP_MAX_DISP_NUM_BUFF 4096
+
 #define KMP_MAX_ORDERED 8
 
 #define KMP_MAX_FIELDS 32


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