/* -----------------------------------------------------------------------------
- * $Id: StgStorage.h,v 1.5 1999/11/02 15:05:53 simonmar Exp $
+ * $Id: StgStorage.h,v 1.6 1999/11/09 15:47:09 simonmar Exp $
*
* (c) The GHC Team, 1998-1999
*
#ifndef STGSTORAGE_H
#define STGSTORAGE_H
+/* GENERATION GC NOTES
+ *
+ * We support an arbitrary number of generations, with an arbitrary number
+ * of steps per generation. Notes (in no particular order):
+ *
+ * - all generations except the oldest should have two steps. This gives
+ * objects a decent chance to age before being promoted, and in
+ * particular will ensure that we don't end up with too many
+ * thunks being updated in older generations.
+ *
+ * - the oldest generation has one step. There's no point in aging
+ * objects in the oldest generation.
+ *
+ * - generation 0, step 0 (G0S0) is the allocation area. It is given
+ * a fixed set of blocks during initialisation, and these blocks
+ * are never freed.
+ *
+ * - during garbage collection, each step which is an evacuation
+ * destination (i.e. all steps except G0S0) is allocated a to-space.
+ * evacuated objects are allocated into the step's to-space until
+ * GC is finished, when the original step's contents may be freed
+ * and replaced by the to-space.
+ *
+ * - the mutable-list is per-generation (not per-step). G0 doesn't
+ * have one (since every garbage collection collects at least G0).
+ *
+ * - block descriptors contain pointers to both the step and the
+ * generation that the block belongs to, for convenience.
+ *
+ * - static objects are stored in per-generation lists. See GC.c for
+ * details of how we collect CAFs in the generational scheme.
+ *
+ * - large objects are per-step, and are promoted in the same way
+ * as small objects, except that we may allocate large objects into
+ * generation 1 initially.
+ */
+
+typedef struct _step {
+ unsigned int no; /* step number */
+ bdescr *blocks; /* blocks in this step */
+ unsigned int n_blocks; /* number of blocks */
+ struct _step *to; /* where collected objects from this step go */
+ struct _generation *gen; /* generation this step belongs to */
+ bdescr *large_objects; /* large objects (doubly linked) */
+
+ /* temporary use during GC: */
+ StgPtr hp; /* next free locn in to-space */
+ StgPtr hpLim; /* end of current to-space block */
+ bdescr *hp_bd; /* bdescr of current to-space block */
+ bdescr *to_space; /* bdescr of first to-space block */
+ unsigned int to_blocks; /* number of blocks in to-space */
+ bdescr *scan_bd; /* block currently being scanned */
+ StgPtr scan; /* scan pointer in current block */
+ bdescr *new_large_objects; /* large objects collected so far */
+ bdescr *scavenged_large_objects; /* live large objects after GC (dbl link) */
+} step;
+
+typedef struct _generation {
+ unsigned int no; /* generation number */
+ step *steps; /* steps */
+ unsigned int n_steps; /* number of steps */
+ unsigned int max_blocks; /* max blocks in step 0 */
+ StgMutClosure *mut_list; /* mutable objects in this generation (not G0)*/
+ StgMutClosure *mut_once_list; /* objects that point to younger generations */
+
+ /* temporary use during GC: */
+ StgMutClosure *saved_mut_list;
+
+ /* stats information */
+ unsigned int collections;
+ unsigned int failed_promotions;
+} generation;
+
/* -----------------------------------------------------------------------------
Allocation area for compiled code
projects / ghc-hetmet.git / blobdiff