[Openmp-commits] [PATCH] D51624: [libomptarget][CUDA] Use cuDeviceGetAttribute, NFCI.

[Jonas Hahnfeld via Phabricator via Openmp-commits]

Hahnfeld created this revision.
Hahnfeld added reviewers: AlexEichenberger, grokos, gtbercea.
Herald added a subscriber: openmp-commits.

cuDeviceGetProperties has apparently been deprecated since CUDA 5.0.
Nvidia started using annotations only in CUDA 9.2, so nobody noticed
nor cared before.
The new function returns the same values, tested with a https://reviews.llvm.org/P100.


Repository:
  rOMP OpenMP

https://reviews.llvm.org/D51624

Files:
  libomptarget/plugins/cuda/src/rtl.cpp


Index: libomptarget/plugins/cuda/src/rtl.cpp
===================================================================
--- libomptarget/plugins/cuda/src/rtl.cpp
+++ libomptarget/plugins/cuda/src/rtl.cpp
@@ -285,43 +285,48 @@
     return OFFLOAD_FAIL;
   }
 
-  // scan properties to determine number of threads/block and blocks/grid.
-  CUdevprop Properties;
-  err = cuDeviceGetProperties(&Properties, cuDevice);
+  // Query attributes to determine number of threads/block and blocks/grid.
+  int maxGridDimX;
+  err = cuDeviceGetAttribute(&maxGridDimX, CU_DEVICE_ATTRIBUTE_MAX_GRID_DIM_X,
+                             cuDevice);
   if (err != CUDA_SUCCESS) {
-    DP("Error getting device Properties, use defaults\n");
+    DP("Error getting max grid dimension, use default\n");
     DeviceInfo.BlocksPerGrid[device_id] = RTLDeviceInfoTy::DefaultNumTeams;
-    DeviceInfo.ThreadsPerBlock[device_id] = RTLDeviceInfoTy::DefaultNumThreads;
-    DeviceInfo.WarpSize[device_id] = 32;
+  } else if (maxGridDimX <= RTLDeviceInfoTy::HardTeamLimit) {
+    DeviceInfo.BlocksPerGrid[device_id] = maxGridDimX;
+    DP("Using %d CUDA blocks per grid\n", maxGridDimX);
   } else {
-    // Get blocks per grid
-    if (Properties.maxGridSize[0] <= RTLDeviceInfoTy::HardTeamLimit) {
-      DeviceInfo.BlocksPerGrid[device_id] = Properties.maxGridSize[0];
-      DP("Using %d CUDA blocks per grid\n", Properties.maxGridSize[0]);
-    } else {
-      DeviceInfo.BlocksPerGrid[device_id] = RTLDeviceInfoTy::HardTeamLimit;
-      DP("Max CUDA blocks per grid %d exceeds the hard team limit %d, capping "
-          "at the hard limit\n", Properties.maxGridSize[0],
-          RTLDeviceInfoTy::HardTeamLimit);
-    }
+    DeviceInfo.BlocksPerGrid[device_id] = RTLDeviceInfoTy::HardTeamLimit;
+    DP("Max CUDA blocks per grid %d exceeds the hard team limit %d, capping "
+       "at the hard limit\n",
+       maxGridDimX, RTLDeviceInfoTy::HardTeamLimit);
+  }
 
-    // Get threads per block, exploit threads only along x axis
-    if (Properties.maxThreadsDim[0] <= RTLDeviceInfoTy::HardThreadLimit) {
-      DeviceInfo.ThreadsPerBlock[device_id] = Properties.maxThreadsDim[0];
-      DP("Using %d CUDA threads per block\n", Properties.maxThreadsDim[0]);
-      if (Properties.maxThreadsDim[0] < Properties.maxThreadsPerBlock) {
-        DP("(fewer than max per block along all xyz dims %d)\n",
-            Properties.maxThreadsPerBlock);
-      }
-    } else {
-      DeviceInfo.ThreadsPerBlock[device_id] = RTLDeviceInfoTy::HardThreadLimit;
-      DP("Max CUDA threads per block %d exceeds the hard thread limit %d, "
-          "capping at the hard limit\n", Properties.maxThreadsDim[0],
-          RTLDeviceInfoTy::HardThreadLimit);
-    }
+  // We are only exploting threads along the x axis.
+  int maxBlockDimX;
+  err = cuDeviceGetAttribute(&maxBlockDimX, CU_DEVICE_ATTRIBUTE_MAX_BLOCK_DIM_X,
+                             cuDevice);
+  if (err != CUDA_SUCCESS) {
+    DP("Error getting max block dimension, use default\n");
+    DeviceInfo.ThreadsPerBlock[device_id] = RTLDeviceInfoTy::DefaultNumThreads;
+  } else if (maxBlockDimX <= RTLDeviceInfoTy::HardThreadLimit) {
+    DeviceInfo.ThreadsPerBlock[device_id] = maxBlockDimX;
+    DP("Using %d CUDA threads per block\n", maxBlockDimX);
+  } else {
+    DeviceInfo.ThreadsPerBlock[device_id] = RTLDeviceInfoTy::HardThreadLimit;
+    DP("Max CUDA threads per block %d exceeds the hard thread limit %d, capping"
+       "at the hard limit\n",
+       maxBlockDimX, RTLDeviceInfoTy::HardThreadLimit);
+  }
 
-    // According to the documentation, SIMDWidth is "Warp size in threads".
-    DeviceInfo.WarpSize[device_id] = Properties.SIMDWidth;
+  int warpSize;
+  err =
+      cuDeviceGetAttribute(&warpSize, CU_DEVICE_ATTRIBUTE_WARP_SIZE, cuDevice);
+  if (err != CUDA_SUCCESS) {
+    DP("Error getting warp size, assume default\n");
+    DeviceInfo.WarpSize[device_id] = 32;
+  } else {
+    DeviceInfo.WarpSize[device_id] = warpSize;
   }
 
   // Adjust teams to the env variables


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