Invert GPU-GPU direct transfer control environment variable name

doc/doxygen/chapters/environment_variables.doxy

@@ -217,12 +217,12 @@ it is therefore necessary to disable asynchronous data transfers.
 Disable asynchronous copies between CPU and MIC devices.
 </dd>
 
-<dt>STARPU_DISABLE_CUDA_GPU_GPU_DIRECT</dt>
+<dt>STARPU_ENABLE_CUDA_GPU_GPU_DIRECT</dt>
 <dd>
-\anchor STARPU_DISABLE_CUDA_GPU_GPU_DIRECT
-\addindex __env__STARPU_DISABLE_CUDA_GPU_GPU_DIRECT
-Disable direct CUDA transfers from GPU to GPU, and let CUDA copy through RAM
-instead. This permits to test the performance effect of GPU-Direct.
+\anchor STARPU_ENABLE_CUDA_GPU_GPU_DIRECT
+\addindex __env__STARPU_ENABLE_CUDA_GPU_GPU_DIRECT
+Enable direct CUDA transfers from GPU to GPU, without copying through RAM.
+This permits to test the performance effect of GPU-Direct.
 </dd>
 
 </dl>

doc/texinfo/chapters/configuration.texi

@@ -477,9 +477,9 @@ it is therefore necessary to disable asynchronous data transfers.
 Disable asynchronous copies between CPU and MIC devices.
 @end defvr
 
-@defvr {Environment variable} STARPU_DISABLE_CUDA_GPU_GPU_DIRECT
-Disable direct CUDA transfers from GPU to GPU, and let CUDA copy through RAM
-instead. This permits to test the performance effect of GPU-Direct.
+@defvr {Environment variable} STARPU_ENABLE_CUDA_GPU_GPU_DIRECT
+Enable direct CUDA transfers from GPU to GPU, without copying through RAM.
+This permits to test the performance effect of GPU-Direct.
 @end defvr
 
 @node Scheduling

src/core/perfmodel/perfmodel_bus.c

@@ -238,7 +238,7 @@ static void measure_bandwidth_between_dev_and_dev_cuda(int src, int dst)
 	 * since we cleanly shutdown CUDA before returning. */
 	cudaSetDevice(src);
 
-	if (starpu_get_env_number("STARPU_DISABLE_CUDA_GPU_GPU_DIRECT") <= 0)
+	if (starpu_get_env_number("STARPU_ENABLE_CUDA_GPU_GPU_DIRECT") > 0)
 	{
 		cures = cudaDeviceCanAccessPeer(&can, src, dst);
 		if (!cures && can)
@@ -260,7 +260,7 @@ static void measure_bandwidth_between_dev_and_dev_cuda(int src, int dst)
 	 * since we cleanly shutdown CUDA before returning. */
 	cudaSetDevice(dst);
 
-	if (starpu_get_env_number("STARPU_DISABLE_CUDA_GPU_GPU_DIRECT") <= 0)
+	if (starpu_get_env_number("STARPU_ENABLE_CUDA_GPU_GPU_DIRECT") > 0)
 	{
 		cures = cudaDeviceCanAccessPeer(&can, dst, src);
 		if (!cures && can)

src/drivers/cuda/driver_cuda.c

@@ -200,7 +200,7 @@ static void init_context(unsigned devid)
 	starpu_cuda_set_device(devid);
 
 #ifdef HAVE_CUDA_MEMCPY_PEER
-	if (starpu_get_env_number("STARPU_DISABLE_CUDA_GPU_GPU_DIRECT") == 0)
+	if (starpu_get_env_number("STARPU_ENABLE_CUDA_GPU_GPU_DIRECT") > 0)
 	{
 		int nworkers = starpu_worker_get_count();
 		for (workerid = 0; workerid < nworkers; workerid++)