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ggml-alloc : fix leak when reusing a tensor with a larger size #16679

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Merged
merged 1 commit into from
Oct 20, 2025
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ggml-alloc : fix leak when reusing a tensor with a larger size #16679

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22 changes: 22 additions & 0 deletions ggml/src/ggml-alloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -598,6 +598,26 @@ static bool ggml_gallocr_is_allocated(ggml_gallocr_t galloc, struct ggml_tensor
return t->data != NULL || ggml_gallocr_hash_get(galloc, t)->allocated;
}

// free the extra space at the end if the new tensor is smaller
static void ggml_gallocr_free_extra_space(ggml_gallocr_t galloc, struct ggml_tensor * node, struct ggml_tensor * parent) {
struct hash_node * hn = ggml_gallocr_hash_get(galloc, node);
struct hash_node * p_hn = ggml_gallocr_hash_get(galloc, parent);

size_t parent_size = ggml_backend_buft_get_alloc_size(galloc->bufts[p_hn->buffer_id], parent);
size_t node_size = ggml_backend_buft_get_alloc_size(galloc->bufts[hn->buffer_id], node);

GGML_ASSERT(parent_size >= node_size);

if (parent_size > node_size) {
struct ggml_dyn_tallocr * p_alloc = galloc->buf_tallocs[p_hn->buffer_id];
struct buffer_address p_addr = p_hn->addr;
p_addr.offset += node_size;
size_t extra_size = parent_size - node_size;
AT_PRINTF("freeing extra %zu bytes from parent %s for %s\n", extra_size, parent->name, node->name);
ggml_dyn_tallocr_free_tensor(p_alloc, p_addr, extra_size, parent);
}
}

static void ggml_gallocr_allocate_node(ggml_gallocr_t galloc, struct ggml_tensor * node, int buffer_id) {
GGML_ASSERT(buffer_id >= 0);
struct hash_node * hn = ggml_gallocr_hash_get(galloc, node);
Expand Down Expand Up @@ -643,13 +663,15 @@ static void ggml_gallocr_allocate_node(ggml_gallocr_t galloc, struct ggml_tensor
hn->addr = p_hn->addr;
p_hn->allocated = false; // avoid freeing the parent
view_src_hn->allocated = false;
ggml_gallocr_free_extra_space(galloc, node, view_src);
return;
}
} else {
AT_PRINTF("reusing parent %s for %s\n", parent->name, node->name);
hn->buffer_id = p_hn->buffer_id;
hn->addr = p_hn->addr;
p_hn->allocated = false; // avoid freeing the parent
ggml_gallocr_free_extra_space(galloc, node, parent);
return;
}
}
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