From: Jeremy Demeule <redacted>
Date: Mon, 15 Dec 2025 14:14:49 +0000 (+0100)
Subject: metal: use shared buffers on eGPU (llama/17866)
X-Git-Tag: upstream/0.9.4.395~4
X-Git-Url: https://git.djapps.eu/?a=commitdiff_plain;h=0b5b649efcd1c6dbd65723c244e24e863cfab97e;p=pkg%2Fggml%2Fsources%2Fggml

metal: use shared buffers on eGPU (llama/17866)

* metal: use shared buffers on eGPU

With #15906, I noticed on important regression when using metal backend on eGPU.
This commit restore the previous behavior and add an option to force its activation.

* metal: use shared buffers on eGPU

* metal: use shared buffers on eGPU
---

diff --git a/src/ggml-metal/ggml-metal-device.m b/src/ggml-metal/ggml-metal-device.m
index 7b7d1c12..f24270bb 100644
--- a/src/ggml-metal/ggml-metal-device.m
+++ b/src/ggml-metal/ggml-metal-device.m
@@ -769,9 +769,16 @@ ggml_metal_device_t ggml_metal_device_init(void) {
 #endif
 
             dev->props.use_shared_buffers = dev->props.has_unified_memory;
+#if TARGET_OS_OSX
+            // In case of eGPU, shared memory may be preferable.
+            dev->props.use_shared_buffers |= [dev->mtl_device location] == MTLDeviceLocationExternal;
+#endif
             if (getenv("GGML_METAL_SHARED_BUFFERS_DISABLE") != NULL) {
                 dev->props.use_shared_buffers = false;
             }
+            if (getenv("GGML_METAL_SHARED_BUFFERS_ENABLE") != NULL) {
+                dev->props.use_shared_buffers = true;
+            }
 
             dev->props.supports_gpu_family_apple7 = [dev->mtl_device supportsFamily:MTLGPUFamilyApple7];