metal : use shared buffers between CPU and GPU (ggerganov#1696)

* Use MTLDevice.newBufferWithBytesNoCopy to share buffers between CPU and GPU

* Page-align buffers used by Metal

* Remove trailing whitespace

* Only import unistd.h for Metal builds

* metal : remove unnecessary copies

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

ggml-metal.m

@@ -195,14 +195,25 @@ bool ggml_metal_add_buffer(
             }
         }
 
+        size_t page_size = getpagesize();
+        size_t aligned_size = size;
+        if ((aligned_size % page_size) != 0) {
+            aligned_size += (page_size - (aligned_size % page_size));
+        }
+
         ctx->buffers[ctx->n_buffers].name = name;
         ctx->buffers[ctx->n_buffers].data = data;
         ctx->buffers[ctx->n_buffers].size = size;
-        ctx->buffers[ctx->n_buffers].metal = [ctx->device newBufferWithBytes:data length:size options:MTLResourceStorageModeShared];
+        ctx->buffers[ctx->n_buffers].metal = [ctx->device newBufferWithBytesNoCopy:data length:aligned_size options:MTLResourceStorageModeShared deallocator:nil];
 
-        ++ctx->n_buffers;
+        if (ctx->buffers[ctx->n_buffers].metal == nil) {
+            fprintf(stderr, "%s: failed to allocate '%-16s' buffer, size = %8.2f MB\n", __func__, name, aligned_size / 1024.0 / 1024.0);
+            return false;
+        } else {
+            fprintf(stderr, "%s: allocated '%-16s' buffer, size = %8.2f MB\n", __func__, name, aligned_size / 1024.0 / 1024.0);
+        }
 
-        fprintf(stderr, "%s: allocated '%-16s' buffer, size = %8.2f MB\n", __func__, name, size / 1024.0 / 1024.0);
+        ++ctx->n_buffers;
     }
 
     return true;

ggml.c

@@ -22,6 +22,10 @@
 #include <float.h>
 #include <limits.h>
 
+#ifdef GGML_USE_METAL
+#include <unistd.h>
+#endif
+
 // if C99 - static_assert is noop
 // ref: https://stackoverflow.com/a/53923785/4039976
 #ifndef static_assert
@@ -122,7 +126,11 @@ typedef void* thread_ret_t;
 #else
 inline static void* ggml_aligned_malloc(size_t size) {
     void* aligned_memory = NULL;
+#ifdef GGML_USE_METAL
+    int result = posix_memalign(&aligned_memory, getpagesize(), size);
+#else
     int result = posix_memalign(&aligned_memory, GGML_MEM_ALIGN, size);
+#endif
     if (result != 0) {
         // Handle allocation failure
         return NULL;

llama-util.h

@@ -405,13 +405,29 @@ struct llama_buffer {
     llama_buffer() = default;
 
     void resize(size_t len) {
+#ifdef GGML_USE_METAL
+        free(addr);
+        int result = posix_memalign((void **) &addr, getpagesize(), len);
+        if (result == 0) {
+            memset(addr, 0, len);
+        }
+        else {
+            addr = NULL;
+        }
+#else
         delete[] addr;
         addr = new uint8_t[len];
+#endif
         size = len;
     }
 
     ~llama_buffer() {
+#ifdef GGML_USE_METAL
+        free(addr);
+#else
         delete[] addr;
+#endif
+        addr = NULL;
     }
 
     // disable copy and move

llama.cpp

@@ -53,7 +53,6 @@ enum e_model {
     MODEL_65B,
 };
 
-
 static const size_t MB = 1024*1024;
 
 // computed for n_ctx == 2048
@@ -1281,12 +1280,6 @@ static bool llama_eval_internal(
     ggml_set_name(embd, "embd");
     memcpy(embd->data, tokens, N*ggml_element_size(embd));
 
-#ifdef GGML_USE_METAL
-    if (lctx.ctx_metal && N == 1) {
-        ggml_metal_set_tensor(lctx.ctx_metal, embd);
-    }
-#endif
-
     struct ggml_tensor * cur;
     struct ggml_tensor * inpL = ggml_get_rows(ctx0, model.tok_embeddings, embd);
 
@@ -1484,12 +1477,6 @@ static bool llama_eval_internal(
         }
 
         ggml_graph_compute(ctx0, &gf);
-
-        if (lctx.ctx_metal) {
-            // We need to sync the CPU KV cache with the GPU KV cache
-            ggml_metal_set_tensor(lctx.ctx_metal, kv_self.k);
-            ggml_metal_set_tensor(lctx.ctx_metal, kv_self.v);
-        }
     }
 #else
     ggml_graph_compute(ctx0, &gf);