/**
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* \file
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* Copy functions for nursery collections.
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*
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* Copyright 2001-2003 Ximian, Inc
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* Copyright 2003-2010 Novell, Inc.
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* Copyright (C) 2012 Xamarin Inc
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*
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* Licensed under the MIT license. See LICENSE file in the project root for full license information.
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*/
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#undef SERIAL_COPY_OBJECT
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#undef SERIAL_COPY_OBJECT_FROM_OBJ
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#if defined(SGEN_SIMPLE_NURSERY)
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#ifdef SGEN_SIMPLE_PAR_NURSERY
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#ifdef SGEN_CONCURRENT_MAJOR
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#define SERIAL_COPY_OBJECT simple_par_nursery_with_concurrent_major_copy_object
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#define SERIAL_COPY_OBJECT_FROM_OBJ simple_par_nursery_with_concurrent_major_copy_object_from_obj
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#else
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#define SERIAL_COPY_OBJECT simple_par_nursery_copy_object
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#define SERIAL_COPY_OBJECT_FROM_OBJ simple_par_nursery_copy_object_from_obj
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#endif
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#else
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#ifdef SGEN_CONCURRENT_MAJOR
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#define SERIAL_COPY_OBJECT simple_nursery_serial_with_concurrent_major_copy_object
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#define SERIAL_COPY_OBJECT_FROM_OBJ simple_nursery_serial_with_concurrent_major_copy_object_from_obj
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#else
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#define SERIAL_COPY_OBJECT simple_nursery_serial_copy_object
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#define SERIAL_COPY_OBJECT_FROM_OBJ simple_nursery_serial_copy_object_from_obj
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#endif
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#endif
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#elif defined (SGEN_SPLIT_NURSERY)
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#ifdef SGEN_CONCURRENT_MAJOR
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#define SERIAL_COPY_OBJECT split_nursery_serial_with_concurrent_major_copy_object
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#define SERIAL_COPY_OBJECT_FROM_OBJ split_nursery_serial_with_concurrent_major_copy_object_from_obj
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#else
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#define SERIAL_COPY_OBJECT split_nursery_serial_copy_object
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#define SERIAL_COPY_OBJECT_FROM_OBJ split_nursery_serial_copy_object_from_obj
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#endif
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#else
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#error "No nursery configuration specified"
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#endif
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extern guint64 stat_nursery_copy_object_failed_to_space; /* from sgen-gc.c */
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/*
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* This is how the copying happens from the nursery to the old generation.
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* We assume that at this time all the pinned objects have been identified and
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* marked as such.
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* We run scan_object() for each pinned object so that each referenced
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* objects if possible are copied. The new gray objects created can have
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* scan_object() run on them right away, too.
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* Then we run copy_object() for the precisely tracked roots. At this point
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* all the roots are either gray or black. We run scan_object() on the gray
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* objects until no more gray objects are created.
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* At the end of the process we walk again the pinned list and we unmark
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* the pinned flag. As we go we also create the list of free space for use
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* in the next allocation runs.
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*
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* We need to remember objects from the old generation that point to the new one
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* (or just addresses?).
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*
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* copy_object could be made into a macro once debugged (use inline for now).
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*/
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static MONO_ALWAYS_INLINE void
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SERIAL_COPY_OBJECT (GCObject **obj_slot, SgenGrayQueue *queue)
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{
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GCObject *forwarded;
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GCObject *copy;
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GCObject *obj = *obj_slot;
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SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy from a %d generation collection", current_collection_generation);
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HEAVY_STAT (++stat_copy_object_called_nursery);
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if (!sgen_ptr_in_nursery (obj)) {
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HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
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return;
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}
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SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);
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/*
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* Before we can copy the object we must make sure that we are
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* allowed to, i.e. that the object not pinned, not already
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* forwarded or belongs to the nursery To Space.
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*/
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if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
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SGEN_ASSERT (9, sgen_obj_get_descriptor (forwarded), "forwarded object %p has no gc descriptor", forwarded);
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SGEN_LOG (9, " (already forwarded to %p)", forwarded);
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HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
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SGEN_UPDATE_REFERENCE (obj_slot, forwarded);
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return;
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}
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if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
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SGEN_ASSERT (9, sgen_vtable_get_descriptor (SGEN_LOAD_VTABLE(obj)), "pinned object %p has no gc descriptor", obj);
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SGEN_LOG (9, " (pinned, no change)");
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HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
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return;
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}
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#ifndef SGEN_SIMPLE_NURSERY
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if (sgen_nursery_is_to_space (obj)) {
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SGEN_ASSERT (9, sgen_vtable_get_descriptor (SGEN_LOAD_VTABLE(obj)), "to space object %p has no gc descriptor", obj);
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SGEN_LOG (9, " (tospace, no change)");
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HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
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return;
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}
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#endif
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HEAVY_STAT (++stat_objects_copied_nursery);
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#ifdef SGEN_SIMPLE_PAR_NURSERY
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copy = copy_object_no_checks_par (obj, queue);
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#else
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copy = copy_object_no_checks (obj, queue);
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#endif
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SGEN_UPDATE_REFERENCE (obj_slot, copy);
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}
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/*
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* SERIAL_COPY_OBJECT_FROM_OBJ:
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*
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* Similar to SERIAL_COPY_OBJECT, but assumes that OBJ_SLOT is part of an object, so it handles global remsets as well.
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*/
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static MONO_ALWAYS_INLINE void
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SERIAL_COPY_OBJECT_FROM_OBJ (GCObject **obj_slot, SgenGrayQueue *queue)
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{
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GCObject *forwarded;
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GCObject *obj = *obj_slot;
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GCObject *copy;
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SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy-from-obj from a %d generation collection", current_collection_generation);
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HEAVY_STAT (++stat_copy_object_called_nursery);
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if (!sgen_ptr_in_nursery (obj)) {
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HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
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return;
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}
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SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);
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/*
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* Before we can copy the object we must make sure that we are
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* allowed to, i.e. that the object not pinned, not already
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* forwarded or belongs to the nursery To Space.
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*/
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if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
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SGEN_ASSERT (9, sgen_obj_get_descriptor (forwarded), "forwarded object %p has no gc descriptor", forwarded);
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SGEN_LOG (9, " (already forwarded to %p)", forwarded);
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HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
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#ifdef SGEN_CONCURRENT_MAJOR
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/* See comment on STORE_STORE_FENCE below. */
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STORE_STORE_FENCE;
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#endif
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SGEN_UPDATE_REFERENCE (obj_slot, forwarded);
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#ifndef SGEN_SIMPLE_NURSERY
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if (G_UNLIKELY (sgen_ptr_in_nursery (forwarded) && !sgen_ptr_in_nursery (obj_slot) && !SGEN_OBJECT_IS_CEMENTED (forwarded)))
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sgen_add_to_global_remset (obj_slot, forwarded);
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#endif
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return;
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}
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if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
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SGEN_ASSERT (9, sgen_vtable_get_descriptor (SGEN_LOAD_VTABLE(obj)), "pinned object %p has no gc descriptor", obj);
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SGEN_LOG (9, " (pinned, no change)");
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HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
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if (!sgen_ptr_in_nursery (obj_slot) && !SGEN_OBJECT_IS_CEMENTED (obj))
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sgen_add_to_global_remset (obj_slot, obj);
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return;
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}
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#ifndef SGEN_SIMPLE_NURSERY
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if (sgen_nursery_is_to_space (obj)) {
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/* FIXME: all of these could just use `sgen_obj_get_descriptor_safe()` */
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SGEN_ASSERT (9, sgen_vtable_get_descriptor (SGEN_LOAD_VTABLE(obj)), "to space object %p has no gc descriptor", obj);
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SGEN_LOG (9, " (tospace, no change)");
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HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
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/*
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* FIXME:
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*
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* The card table scanning code sometimes clears cards
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* that have just been set for a global remset. In
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* the split nursery the following situation can
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* occur:
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*
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* Let's say object A starts in card C but continues
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* into C+1. Within A, at offset O there's a
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* reference to a new nursery object X. A+O is in
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* card C+1. Now card C is scanned, and as part of
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* it, object A. The reference at A+O is processed by
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* copying X into nursery to-space at Y. Since it's
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* still in the nursery, a global remset must be added
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* for A+O, so card C+1 is marked. Now, however, card
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* C+1 is scanned, which means that it's cleared
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* first. This wouldn't be terribly bad if reference
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* A+O were re-scanned and the global remset re-added,
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* but since the reference points to to-space, that
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* doesn't happen, and C+1 remains cleared: the remset
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* is lost.
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*
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* There's at least two ways to fix this. The easy
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* one is to re-add the remset on the re-scan. This
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* is that - the following two lines of code.
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*
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* The proper solution appears to be to first make a
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* copy of the cards before scanning a block, then to
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* clear all the cards and scan from the copy, so no
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* remsets will be overwritten. Scanning objects at
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* most once would be the icing on the cake.
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*/
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if (!sgen_ptr_in_nursery (obj_slot) && !SGEN_OBJECT_IS_CEMENTED (obj))
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sgen_add_to_global_remset (obj_slot, obj);
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return;
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}
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#endif
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HEAVY_STAT (++stat_objects_copied_nursery);
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#ifdef SGEN_SIMPLE_PAR_NURSERY
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copy = copy_object_no_checks_par (obj, queue);
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#else
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copy = copy_object_no_checks (obj, queue);
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#endif
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#ifdef SGEN_CONCURRENT_MAJOR
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/*
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* If an object is evacuated to the major heap and a reference to it, from the major
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* heap, updated, the concurrent major collector might follow that reference and
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* scan the new major object. To make sure the object contents are seen by the
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* major collector we need this write barrier, so that the reference is seen after
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* the object.
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*/
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STORE_STORE_FENCE;
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#endif
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SGEN_UPDATE_REFERENCE (obj_slot, copy);
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#ifndef SGEN_SIMPLE_NURSERY
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if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot) && !SGEN_OBJECT_IS_CEMENTED (copy)))
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sgen_add_to_global_remset (obj_slot, copy);
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#else
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/* copy_object_no_checks () can return obj on OOM */
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if (G_UNLIKELY (obj == copy)) {
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if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot) && !SGEN_OBJECT_IS_CEMENTED (copy)))
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sgen_add_to_global_remset (obj_slot, copy);
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}
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#endif
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}
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