Mono Continuations - Memory keeps increasing after store()

Question

Hi,

Here's Mono Continuations' continuation_store (...). From looking at the code below, it appears as though store() follows these two branches:

1. cont->saved_stack && num_bytes <= cont->stack_alloc_size
   • use the memory directly
2. else
   • gc free the used memory, and create some new memory.

However, the weird thing is if I repeatedly use continuation_store(), the memory usage increases until at a later step a huge and laggy GC operation is done. Can anyone explain why this happens?

Thanks

static int
continuation_store (MonoContinuation *cont, int state, MonoException **e)
{
    MonoLMF *lmf = mono_get_lmf ();
    gsize num_bytes;

    if (!cont->domain)
     *e =  mono_get_exception_argument ("cont", "Continuation not initialized");
    if (cont->domain != mono_domain_get () || cont->thread_id != GetCurrentThreadId ())
     *e = mono_get_exception_argument ("cont", "Continuation from another thread or domain");

    cont->lmf = lmf;
    cont->return_ip = __builtin_return_address (0);
    cont->return_sp = __builtin_frame_address (0);

    num_bytes = (char*)cont->top_sp - (char*)cont->return_sp;

    /*g_print ("store: %d bytes, sp: %p, ip: %p, lmf: %p\n", num_bytes, cont->return_sp, cont->return_ip, lmf);*/

    if (cont->saved_stack && num_bytes <= cont->stack_alloc_size) 
    {
     /* clear to avoid GC retention */
     if (num_bytes < cont->stack_used_size)
      memset ((char*)cont->saved_stack + num_bytes, 0, cont->stack_used_size - num_bytes);
    } 
    else 
    {
     tasklets_lock ();
     internal_init ();
     if (cont->saved_stack) {
      mono_g_hash_table_remove (keepalive_stacks, cont->saved_stack);
      mono_gc_free_fixed (cont->saved_stack);
     }
     cont->stack_used_size = num_bytes;
     cont->stack_alloc_size = num_bytes * 1.1;
     cont->saved_stack = mono_gc_alloc_fixed (cont->stack_alloc_size, NULL);
     mono_g_hash_table_insert (keepalive_stacks, cont->saved_stack, cont->saved_stack);
     tasklets_unlock ();
    }
    memcpy (cont->saved_stack, cont->return_sp, num_bytes);

    return state;
}