From 0710d5f0f83755202af4fb451430ad0531bc35e8 Mon Sep 17 00:00:00 2001
From: slaren <slarengh@gmail.com>
Date: Fri, 14 Nov 2025 22:04:41 +0100
Subject: [PATCH] ggml : add GGML_SCHED_NO_REALLOC option to disable
 reallocations in ggml_backend_sched Enabled in ggml-ci for testing.

---
 ci/run.sh                 |  2 +-
 ggml/CMakeLists.txt       |  1 +
 ggml/src/CMakeLists.txt   |  4 ++++
 ggml/src/ggml-alloc.c     | 11 ++++++++---
 ggml/src/ggml-backend.cpp |  5 +++++
 tests/CMakeLists.txt      |  2 +-
 6 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/ci/run.sh b/ci/run.sh
index 3fec8e9110f0a..6e225157c9b75 100755
--- a/ci/run.sh
+++ b/ci/run.sh
@@ -45,7 +45,7 @@ sd=`dirname $0`
 cd $sd/../
 SRC=`pwd`
 
-CMAKE_EXTRA="-DLLAMA_FATAL_WARNINGS=ON -DLLAMA_CURL=ON"
+CMAKE_EXTRA="-DLLAMA_FATAL_WARNINGS=ON -DLLAMA_CURL=ON -DGGML_SCHED_NO_REALLOC=ON"
 
 if [ ! -z ${GG_BUILD_METAL} ]; then
     CMAKE_EXTRA="${CMAKE_EXTRA} -DGGML_METAL=ON"
diff --git a/ggml/CMakeLists.txt b/ggml/CMakeLists.txt
index 869796f0e3be6..1e2d517ede877 100644
--- a/ggml/CMakeLists.txt
+++ b/ggml/CMakeLists.txt
@@ -182,6 +182,7 @@ endif()
 # ggml core
 set(GGML_SCHED_MAX_COPIES  "4" CACHE STRING "ggml: max input copies for pipeline parallelism")
 option(GGML_CPU                             "ggml: enable CPU backend"                        ON)
+option(GGML_SCHED_NO_REALLOC                "ggml: disallow reallocations in ggml-alloc (for debugging)" OFF)
 
 # 3rd party libs / backends
 option(GGML_ACCELERATE                      "ggml: enable Accelerate framework"               ON)
diff --git a/ggml/src/CMakeLists.txt b/ggml/src/CMakeLists.txt
index 628db3fd65575..bc9b84f2a8635 100644
--- a/ggml/src/CMakeLists.txt
+++ b/ggml/src/CMakeLists.txt
@@ -221,6 +221,10 @@ if (GGML_BACKEND_DL)
     target_compile_definitions(ggml-base PUBLIC GGML_BACKEND_DL)
 endif()
 
+if (GGML_SCHED_NO_REALLOC)
+    target_compile_definitions(ggml-base PUBLIC GGML_SCHED_NO_REALLOC)
+endif()
+
 add_library(ggml
             ggml-backend-reg.cpp)
 add_library(ggml::ggml ALIAS ggml)
diff --git a/ggml/src/ggml-alloc.c b/ggml/src/ggml-alloc.c
index 91aff205f1832..218222ece8726 100644
--- a/ggml/src/ggml-alloc.c
+++ b/ggml/src/ggml-alloc.c
@@ -921,10 +921,15 @@ bool ggml_gallocr_reserve_n(ggml_gallocr_t galloc, struct ggml_cgraph * graph, c
         }
         if (realloc) {
 #ifndef NDEBUG
-            size_t cur_size = galloc->buffers[i] ? ggml_vbuffer_size(galloc->buffers[i]) : 0;
-            GGML_LOG_DEBUG("%s: reallocating %s buffer from size %.02f MiB to %.02f MiB\n", __func__, ggml_backend_buft_name(galloc->bufts[i]), cur_size / 1024.0 / 1024.0, new_size / 1024.0 / 1024.0);
+            {
+                size_t cur_size = galloc->buffers[i] ? ggml_vbuffer_size(galloc->buffers[i]) : 0;
+                if (cur_size > 0) {
+                    GGML_LOG_DEBUG("%s: reallocating %s buffer from size %.02f MiB to %.02f MiB\n",
+                        __func__, ggml_backend_buft_name(galloc->bufts[i]),
+                        cur_size / 1024.0 / 1024.0, new_size / 1024.0 / 1024.0);
+                }
+            }
 #endif
-
             ggml_vbuffer_free(galloc->buffers[i]);
             galloc->buffers[i] = ggml_vbuffer_alloc(galloc->bufts[i], galloc->buf_tallocs[i], GGML_BACKEND_BUFFER_USAGE_COMPUTE);
             if (galloc->buffers[i] == NULL) {
diff --git a/ggml/src/ggml-backend.cpp b/ggml/src/ggml-backend.cpp
index eeaf35c169fac..98ea167cf5429 100644
--- a/ggml/src/ggml-backend.cpp
+++ b/ggml/src/ggml-backend.cpp
@@ -1400,9 +1400,14 @@ static bool ggml_backend_sched_alloc_splits(ggml_backend_sched_t sched) {
         for (int i = 0; i < sched->n_backends; i++) {
             ggml_backend_synchronize(sched->backends[i]);
         }
+#ifdef GGML_SCHED_NO_REALLOC
+        GGML_ABORT("%s: failured to allocate graph, but graph re-allocation is disabled by GGML_SCHED_NO_REALLOC\n", __func__);
+#endif
+
 #ifndef NDEBUG
         GGML_LOG_DEBUG("%s: failed to allocate graph, reserving (backend_ids_changed = %d)\n", __func__, backend_ids_changed);
 #endif
+
         ggml_gallocr_reserve_n(sched->galloc, &sched->graph, sched->node_backend_ids, sched->leaf_backend_ids);
         if (!ggml_gallocr_alloc_graph(sched->galloc, &sched->graph)) {
             GGML_LOG_ERROR("%s: failed to allocate graph\n", __func__);
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d9cc5e933f4ce..9361a113a19bf 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -196,7 +196,7 @@ if (NOT WIN32)
     llama_build_and_test(test-arg-parser.cpp)
 endif()
 
-if (NOT LLAMA_SANITIZE_ADDRESS)
+if (NOT LLAMA_SANITIZE_ADDRESS AND NOT GGML_SCHED_NO_REALLOC)
   # TODO: repair known memory leaks
   llama_build_and_test(test-opt.cpp)
 endif()