Add mmap support for model files

ggml.c

@@ -2529,6 +2529,7 @@ struct ggml_context {
     void * mem_buffer;
     bool   mem_buffer_owned;
     bool   mem_buffer_mlocked;
+    bool   no_alloc;
 
     int    n_objects;
 
@@ -2815,6 +2816,7 @@ struct ggml_context * ggml_init(struct ggml_init_params params) {
         /*.mem_buffer         =*/ params.mem_buffer ? params.mem_buffer : malloc(params.mem_size),
         /*.mem_buffer_owned   =*/ params.mem_buffer ? false : true,
         /*.mem_buffer_mlocked =*/ false,
+        /*.no_alloc           =*/ params.no_alloc,
         /*.n_objects          =*/ 0,
         /*.objects_begin      =*/ NULL,
         /*.objects_end        =*/ NULL,
@@ -2930,7 +2932,7 @@ struct ggml_tensor * ggml_new_tensor_impl(
 
     size_t size_needed = 0;
 
-    if (data == NULL) {
+    if (data == NULL && !ctx->no_alloc) {
         size_needed += GGML_TYPE_SIZE[type]*(ne[0]/GGML_BLCK_SIZE[type]);
         for (int i = 1; i < n_dims; i++) {
             size_needed *= ne[i];
@@ -3014,7 +3016,7 @@ struct ggml_tensor * ggml_new_tensor_impl(
         /*.perf_runs    =*/ 0,
         /*.perf_cycles  =*/ 0,
         /*.perf_time_us =*/ 0,
-        /*.data         =*/ data == NULL ? (void *)(result + 1) : data,
+        /*.data         =*/ (data == NULL && !ctx->no_alloc) ? (void *)(result + 1) : data,
         /*.pad          =*/ { 0 },
     };
 
@@ -10277,6 +10279,7 @@ enum ggml_opt_result ggml_opt(
         struct ggml_init_params params_ctx = {
             .mem_size   = 16*1024*1024,
             .mem_buffer = NULL,
+            .no_alloc   = false,
         };
 
         ctx = ggml_init(params_ctx);

ggml.h

@@ -316,6 +316,7 @@ struct ggml_init_params {
     // memory pool
     size_t mem_size;   // bytes
     void * mem_buffer; // if NULL, memory will be allocated internally
+    bool   no_alloc;   // don't allocate memory for the tensor data
 };
 
 void    ggml_time_init(void); // call this once at the beginning of the program

llama.cpp

@@ -12,6 +12,13 @@
 #include <cassert>
 #include <cstring>
 
+// headers for POSIX mmap
+#if defined (__unix__) || defined (__APPLE__)
+#   include <sys/mman.h>
+#   include <fcntl.h>
+#   include <unistd.h>
+#endif
+
 #define LLAMA_USE_SCRATCH
 #define LLAMA_MAX_SCRATCH_BUFFERS 16
 
@@ -246,6 +253,7 @@ static bool kv_cache_init(
     struct ggml_init_params params;
     params.mem_size   = cache.buf.size();
     params.mem_buffer = cache.buf.data();
+    params.no_alloc   = false;
 
     cache.ctx = ggml_init(params);
 
@@ -288,6 +296,26 @@ struct llama_context_params llama_context_default_params() {
 // model loading
 //
 
+void * mmap_file(const char* fname) {
+#if defined(MAP_FAILED)
+    // POSIX mmap
+    int fd = open(fname, O_RDONLY);
+    size_t len = lseek(fd, 0, SEEK_END);
+    void * mm_addr = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
+    if (mm_addr == MAP_FAILED) {
+        perror("mmap failed");
+        mm_addr = NULL;
+    }
+    close(fd);
+    return mm_addr;
+#else
+    // TODO: windows support
+    (void)(fname); // suppress warnings
+    return NULL;
+#endif
+}
+
+
 static bool llama_model_load(
         const std::string & fname,
         llama_context & lctx,
@@ -303,6 +331,7 @@ static bool llama_model_load(
 
     lctx.t_start_us = t_start_us;
 
+    // TODO: this could probably be smaller when using mmap
     std::vector<char> f_buf(1024*1024);
 
     auto & model = lctx.model;
@@ -449,18 +478,30 @@ static bool llama_model_load(
                 }
     }
 
+    bool use_mmap = (n_parts == 1);
+
+    // try to memory map the model file
+    void* mm_addr = NULL;
+    if (use_mmap) {
+        mm_addr = mmap_file(fname.c_str());
+        if (mm_addr == NULL) {
+            use_mmap = false;
+        }
+    }
+
+
+
     auto & ctx = model.ctx;
 
     size_t ctx_size = 0;
-
     {
         const auto & hparams = model.hparams;
 
         const int n_embd  = hparams.n_embd;
         const int n_layer = hparams.n_layer;
-        const int n_ctx   = hparams.n_ctx;
         const int n_vocab = hparams.n_vocab;
 
+        if (!use_mmap) {
             ctx_size += n_embd*n_vocab*ggml_type_sizef(vtype); // tok_embeddings
 
             ctx_size += n_embd*ggml_type_sizef(GGML_TYPE_F32); // norm
@@ -479,9 +520,7 @@ static bool llama_model_load(
             ctx_size += n_layer*(n_ff*n_embd*ggml_type_sizef(wtype)); // w1
             ctx_size += n_layer*(n_ff*n_embd*ggml_type_sizef(wtype)); // w2
             ctx_size += n_layer*(n_ff*n_embd*ggml_type_sizef(wtype)); // w3
-
-        ctx_size += n_ctx*n_layer*n_embd*ggml_type_sizef(memory_type); // memory_k
-        ctx_size += n_ctx*n_layer*n_embd*ggml_type_sizef(memory_type); // memory_v
+        }
 
         ctx_size += (5 + 10*n_layer)*256; // object overhead
 
@@ -514,6 +553,7 @@ static bool llama_model_load(
         struct ggml_init_params params = {
             /*.mem_size   =*/ lctx.model.buf.size(),
             /*.mem_buffer =*/ lctx.model.buf.data(),
+            /*.no_alloc   =*/ use_mmap,
         };
 
         model.ctx = ggml_init(params);
@@ -595,7 +635,7 @@ static bool llama_model_load(
             fname_part += "." + std::to_string(i);
         }
 
-        fprintf(stderr, "%s: loading model part %d/%d from '%s'\n", __func__, i+1, n_parts, fname_part.c_str());
+        fprintf(stderr, "%s: loading model part %d/%d from '%s'%s\n", __func__, i+1, n_parts, fname_part.c_str(), use_mmap ? " (memory mapped)" : "");
 
         fin = std::ifstream(fname_part, std::ios::binary);
         fin.rdbuf()->pubsetbuf(f_buf.data(), f_buf.size());
@@ -736,7 +776,14 @@ static bool llama_model_load(
                     }
 
                     if (part_id == 0) {
+                        if (mm_addr) {
+                            off_t offset = fin.tellg();
+                            tensor->data = (char *) mm_addr + offset;
+                            fin.seekg(ggml_nbytes(tensor), std::ios::cur);
+                        }
+                        else {
                             fin.read(reinterpret_cast<char *>(tensor->data), ggml_nbytes(tensor));
+                        }
                     } else {
                         fin.seekg(ggml_nbytes(tensor), std::ios::cur);
                     }
@@ -849,6 +896,7 @@ static bool llama_eval_internal(
     struct ggml_init_params params = {
         /*.mem_size   =*/ buf_compute.size(),
         /*.mem_buffer =*/ buf_compute.data(),
+        /*.no_alloc   =*/ false,
     };
 
     struct ggml_context * ctx0 = ggml_init(params);