From: Chenguang Li <redacted>
Date: Wed, 17 Sep 2025 06:33:08 +0000 (+0800)
Subject: CANN: Optimize ggml_cann_set_device (#15935)
X-Git-Tag: upstream/0.0.6527~36
X-Git-Url: https://git.djapps.eu/?a=commitdiff_plain;h=d5fabe3682de515fd09d6c981f7a0d1b75614455;p=pkg%2Fggml%2Fsources%2Fllama.cpp

CANN: Optimize ggml_cann_set_device (#15935)

* CANN: Fix ggml_cann_set_device to avoid redundant device switches

- Added a check to skip aclrtSetDevice if the current device is already set.
- Prevents unnecessary context switches while keeping thread/device consistency.

* CANN: add device default id
---

diff --git a/ggml/src/ggml-cann/common.h b/ggml/src/ggml-cann/common.h
index c5fce8dc..b707b843 100755
--- a/ggml/src/ggml-cann/common.h
+++ b/ggml/src/ggml-cann/common.h
@@ -526,7 +526,10 @@ struct ggml_backend_cann_context {
      */
     aclrtStream stream(int stream) {
         if (streams[stream] == nullptr) {
-            ggml_cann_set_device(device);
+            // If the device is not set here, destroying the stream later may cause a mismatch
+            // between the thread contexts where the stream was created and destroyed.
+            // However, I printed the device_id, thread_id, and stream, and they are all consistent.
+            ACL_CHECK(aclrtSetDevice(device));
             ACL_CHECK(aclrtCreateStream(&streams[stream]));
         }
         return streams[stream];
diff --git a/ggml/src/ggml-cann/ggml-cann.cpp b/ggml/src/ggml-cann/ggml-cann.cpp
index 19a18a28..56d82b4a 100755
--- a/ggml/src/ggml-cann/ggml-cann.cpp
+++ b/ggml/src/ggml-cann/ggml-cann.cpp
@@ -75,13 +75,12 @@
  * @param device The device ID to set.
  */
 void ggml_cann_set_device(const int32_t device) {
-    // TODO: uncomment these lines after empty context has fixed.
-    // int current_device;
-    // ACL_CHECK(aclrtGetDevice(&current_device));
+    int current_device = -1;
+    aclrtGetDevice(&current_device);
 
-    // if (device == current_device) {
-    //   return;
-    // }
+    if (device == current_device) {
+      return;
+    }
     ACL_CHECK(aclrtSetDevice(device));
 }
 
@@ -1729,6 +1728,7 @@ static bool ggml_cann_compute_forward(ggml_backend_cann_context& ctx,
             ggml_cann_get_rows(ctx, dst);
             break;
         case GGML_OP_SET_ROWS:
+            std::cout << "lcg GGML_OP_SET_ROWS"<< std::endl;
             ggml_cann_set_rows(ctx, dst);
             break;
         case GGML_OP_DUP: