what's the meaning of judge whether size leq than IPC_SIZE condition in add_chunk function?

[baildagq]

https://github.com/Project-HAMi/HAMi-core/blob/main/src/allocator/allocator.c#L100

int add_chunk(CUdeviceptr *address,size_t size){
    size_t addr=0;
    size_t allocsize;
    CUresult res = CUDA_SUCCESS;
    CUdevice dev;
    cuCtxGetDevice(&dev);
    if (oom_check(dev,size))
        return -1;
    
    allocated_list_entry *e;
    INIT_ALLOCATED_LIST_ENTRY(e,addr,size);
    if (size <= IPCSIZE)
        res = CUDA_OVERRIDE_CALL(cuda_library_entry,cuMemAlloc_v2,&e->entry->address,size);
    else{
        //size = round_up(size,ALIGN);
        e->entry->length = size;
        res = cuMemoryAllocate(&e->entry->address,size,&e->entry->length,e->entry->allocHandle);
    }
    if (res!=CUDA_SUCCESS){
        LOG_ERROR("cuMemoryAllocate failed res=%d",res);
        return res;
    }
    LIST_ADD(device_overallocated,e);
    //uint64_t t_size;
    *address = e->entry->address;
    allocsize = size;
    cuCtxGetDevice(&dev);
    add_gpu_device_memory_usage(getpid(),dev,allocsize,2);
    return 0;
}

CUresult cuMemoryAllocate(CUdeviceptr* dptr, size_t bytesize, size_t* bytesallocated,void* data){
    CUresult res;
    if (bytesallocated!=NULL)
        *bytesallocated = bytesize;
    res = CUDA_OVERRIDE_CALL(cuda_library_entry,cuMemAlloc_v2,dptr,bytesize);
    return res;
}

I think there is no difference between the implement of size <= IPCSIZE and size > IPCSIZE condition.

what's the meaning of comment //size = round_up(size,ALIGN); ?