[Mono-dev] Mono Continuations - Memory keeps increasing after store()

James Zhao jameszhao00 at gmail.com
Tue Aug 25 20:55:30 EDT 2009

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

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?
If I alloc/free a continuation for roughly each time I call store , the
continuation appears to be GC'ed immediately.

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; }
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