C:/Users/Dennis/src/lang/russell.orig/src/gc/reclaim.c

Go to the documentation of this file.

/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991, 1992 by Xerox Corporation.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to copy this garbage collector for any purpose,
 * provided the above notices are retained on all copies.
 */

#include <stdio.h>
#include "gc_private.h"

signed_word GC_mem_found = 0;
                        /* Number of longwords of memory GC_reclaimed     */

# ifdef FIND_LEAK
static report_leak(p, sz)
ptr_t p;
word sz;
{
    if (HDR(p) -> hb_obj_kind == PTRFREE) {
        GC_err_printf0("Leaked atomic object at ");
    } else {
        GC_err_printf0("Leaked composite object at ");
    }
    if (GC_debugging_started && GC_has_debug_info(p)) {
        GC_print_obj(p);
    } else {
        GC_err_printf1("0x%lx (appr. size = %ld)\n",
                      (unsigned long)WORDS_TO_BYTES(sz));
    }
}

#   define FOUND_FREE(hblk, word_no) \
      if (abort_if_found) { \
         report_leak((long)hblk + WORDS_TO_BYTES(word_no), \
                     HDR(hblk) -> hb_sz); \
      }
# else
#   define FOUND_FREE(hblk, word_no)
# endif

/*
 * reclaim phase
 *
 */


/*
 * Test whether a block is completely empty, i.e. contains no marked
 * objects.  This does not require the block to be in physical
 * memory.
 */
 
bool GC_block_empty(hhdr)
register hdr * hhdr;
{
    register word *p = (word *)(&(hhdr -> hb_marks[0]));
    register word * plim =
                        (word *)(&(hhdr -> hb_marks[MARK_BITS_SZ]));
    while (p < plim) {
        if (*p++) return(FALSE);
    }
    return(TRUE);
}

# ifdef GATHERSTATS
#   define INCR_WORDS(sz) n_words_found += (sz)
# else
#   define INCR_WORDS(sz)
# endif
/*
 * Restore unmarked small objects in h of size sz to the object
 * free list.  Returns the new list.
 * Clears unmarked objects.
 */
/*ARGSUSED*/
ptr_t GC_reclaim_clear(hbp, hhdr, sz, list, abort_if_found)
register struct hblk *hbp;      /* ptr to current heap block            */
register hdr * hhdr;
bool abort_if_found;            /* Abort if a reclaimable object is found */
register ptr_t list;
register word sz;
{
    register int word_no;
    register word *p, *q, *plim;
#   ifdef GATHERSTATS
        register int n_words_found = 0;
#   endif        
    
    p = (word *)(hbp->hb_body);
    word_no = HDR_WORDS;
    plim = (word *)((((word)hbp) + HBLKSIZE)
                   - WORDS_TO_BYTES(sz));

    /* go through all words in block */
        while( p <= plim )  {
            if( mark_bit_from_hdr(hhdr, word_no) ) {
                p += sz;
            } else {
                FOUND_FREE(hbp, word_no);
                INCR_WORDS(sz);
                /* object is available - put on list */
                    obj_link(p) = list;
                    list = ((ptr_t)p);
                /* Clear object, advance p to next object in the process */
                    q = p + sz;
                    p++; /* Skip link field */
                    while (p < q) {
                        *p++ = 0;
                    }
            }
            word_no += sz;
        }
#   ifdef GATHERSTATS
        GC_mem_found += n_words_found;
#   endif
    return(list);
}

/*
 * A special case for 2 word composite objects (e.g. cons cells):
 */
/*ARGSUSED*/
ptr_t GC_reclaim_clear2(hbp, hhdr, list, abort_if_found)
register struct hblk *hbp;      /* ptr to current heap block            */
hdr * hhdr;
bool abort_if_found;            /* Abort if a reclaimable object is found */
register ptr_t list;
{
    register word * mark_word_addr = &(hhdr->hb_marks[divWORDSZ(HDR_WORDS)]);
    register word *p, *plim;
#   ifdef GATHERSTATS
        register int n_words_found = 0;
#   endif
    register int mark_word;
#   define DO_OBJ(start_displ) \
        if (!(mark_word & (1 << start_displ))) { \
            FOUND_FREE(hbp, p - (word *)hbp + start_displ); \
            p[start_displ] = (word)list; \
            list = (ptr_t)(p+start_displ); \
            p[start_displ+1] = 0; \
            INCR_WORDS(2); \
        }
    
    p = (word *)(hbp->hb_body);
    plim = (word *)(((unsigned)hbp) + HBLKSIZE);

    /* go through all words in block */
        while( p < plim )  {
            mark_word = *mark_word_addr++;
            DO_OBJ(0);
            DO_OBJ(2);
            DO_OBJ(4);
            DO_OBJ(6);
            DO_OBJ(8);
            DO_OBJ(10);
            DO_OBJ(12);
            DO_OBJ(14);
            DO_OBJ(16);
            DO_OBJ(18);
            DO_OBJ(20);
            DO_OBJ(22);
            DO_OBJ(24);
            DO_OBJ(26);
            DO_OBJ(28);
            DO_OBJ(30);
            p+=32;
        }               
#   ifdef GATHERSTATS
        GC_mem_found += n_words_found;
#   endif
    return(list);
#   undef DO_OBJ
}

/*
 * Another special case for 4 word composite objects:
 */
/*ARGSUSED*/
ptr_t GC_reclaim_clear4(hbp, hhdr, list, abort_if_found)
register struct hblk *hbp;      /* ptr to current heap block            */
hdr * hhdr;
bool abort_if_found;            /* Abort if a reclaimable object is found */
register ptr_t list;
{
    register word * mark_word_addr = &(hhdr->hb_marks[divWORDSZ(HDR_WORDS)]);
    register word *p, *plim;
#   ifdef GATHERSTATS
        register int n_words_found = 0;
#   endif
    register int mark_word;
#   define DO_OBJ(start_displ) \
        if (!(mark_word & (1 << start_displ))) { \
            FOUND_FREE(hbp, p - (word *)hbp + start_displ); \
            p[start_displ] = (word)list; \
            list = (ptr_t)(p+start_displ); \
            p[start_displ+1] = 0; \
            p[start_displ+2] = 0; \
            p[start_displ+3] = 0; \
            INCR_WORDS(4); \
        }
    
    p = (word *)(hbp->hb_body);
    plim = (word *)(((unsigned)hbp) + HBLKSIZE);

    /* go through all words in block */
        while( p < plim )  {
            mark_word = *mark_word_addr++;
            DO_OBJ(0);
            DO_OBJ(4);
            DO_OBJ(8);
            DO_OBJ(12);
            DO_OBJ(16);
            DO_OBJ(20);
            DO_OBJ(24);
            DO_OBJ(28);
            p+=32;
        }               
#   ifdef GATHERSTATS
        GC_mem_found += n_words_found;
#   endif
    return(list);
#   undef DO_OBJ
}

/* The same thing, but don't clear objects: */
/*ARGSUSED*/
ptr_t GC_reclaim_uninit(hbp, hhdr, sz, list, abort_if_found)
register struct hblk *hbp;      /* ptr to current heap block            */
register hdr * hhdr;
bool abort_if_found;            /* Abort if a reclaimable object is found */
register ptr_t list;
register word sz;
{
    register int word_no;
    register word *p, *plim;
#   ifdef GATHERSTATS
        register int n_words_found = 0;
#   endif
    
    p = (word *)(hbp->hb_body);
    word_no = HDR_WORDS;
    plim = (word *)((((unsigned)hbp) + HBLKSIZE)
                   - WORDS_TO_BYTES(sz));

    /* go through all words in block */
        while( p <= plim )  {
            if( !mark_bit_from_hdr(hhdr, word_no) ) {
                FOUND_FREE(hbp, word_no);
                INCR_WORDS(sz);
                /* object is available - put on list */
                    obj_link(p) = list;
                    list = ((ptr_t)p);
            }
            p += sz;
            word_no += sz;
        }
#   ifdef GATHERSTATS
        GC_mem_found += n_words_found;
#   endif
    return(list);
}

/*
 * Another special case for 2 word atomic objects:
 */
/*ARGSUSED*/
ptr_t GC_reclaim_uninit2(hbp, hhdr, list, abort_if_found)
register struct hblk *hbp;      /* ptr to current heap block            */
hdr * hhdr;
bool abort_if_found;            /* Abort if a reclaimable object is found */
register ptr_t list;
{
    register word * mark_word_addr = &(hhdr->hb_marks[divWORDSZ(HDR_WORDS)]);
    register word *p, *plim;
#   ifdef GATHERSTATS
        register int n_words_found = 0;
#   endif
    register int mark_word;
#   define DO_OBJ(start_displ) \
        if (!(mark_word & (1 << start_displ))) { \
            FOUND_FREE(hbp, p - (word *)hbp + start_displ); \
            p[start_displ] = (word)list; \
            list = (ptr_t)(p+start_displ); \
            INCR_WORDS(2); \
        }
    
    p = (word *)(hbp->hb_body);
    plim = (word *)(((unsigned)hbp) + HBLKSIZE);

    /* go through all words in block */
        while( p < plim )  {
            mark_word = *mark_word_addr++;
            DO_OBJ(0);
            DO_OBJ(2);
            DO_OBJ(4);
            DO_OBJ(6);
            DO_OBJ(8);
            DO_OBJ(10);
            DO_OBJ(12);
            DO_OBJ(14);
            DO_OBJ(16);
            DO_OBJ(18);
            DO_OBJ(20);
            DO_OBJ(22);
            DO_OBJ(24);
            DO_OBJ(26);
            DO_OBJ(28);
            DO_OBJ(30);
            p+=32;
        }               
#   ifdef GATHERSTATS
        GC_mem_found += n_words_found;
#   endif
    return(list);
#   undef DO_OBJ
}

/*
 * Another special case for 4 word atomic objects:
 */
/*ARGSUSED*/
ptr_t GC_reclaim_uninit4(hbp, hhdr, list, abort_if_found)
register struct hblk *hbp;      /* ptr to current heap block            */
hdr * hhdr;
bool abort_if_found;            /* Abort if a reclaimable object is found */
register ptr_t list;
{
    register word * mark_word_addr = &(hhdr->hb_marks[divWORDSZ(HDR_WORDS)]);
    register word *p, *plim;
#   ifdef GATHERSTATS
        register int n_words_found = 0;
#   endif
    register int mark_word;
#   define DO_OBJ(start_displ) \
        if (!(mark_word & (1 << start_displ))) { \
            FOUND_FREE(hbp, p - (word *)hbp + start_displ); \
            p[start_displ] = (word)list; \
            list = (ptr_t)(p+start_displ); \
            INCR_WORDS(4); \
        }
    
    p = (word *)(hbp->hb_body);
    plim = (word *)(((unsigned)hbp) + HBLKSIZE);

    /* go through all words in block */
        while( p < plim )  {
            mark_word = *mark_word_addr++;
            DO_OBJ(0);
            DO_OBJ(4);
            DO_OBJ(8);
            DO_OBJ(12);
            DO_OBJ(16);
            DO_OBJ(20);
            DO_OBJ(24);
            DO_OBJ(28);
            p+=32;
        }               
#   ifdef GATHERSTATS
        GC_mem_found += n_words_found;
#   endif
    return(list);
#   undef DO_OBJ
}

/*
 * Restore unmarked small objects in the block pointed to by hbp
 * to the appropriate object free list.
 * If entirely empty blocks are to be completely deallocated, then
 * caller should perform that check.
 */
GC_reclaim_small_nonempty_block(hbp, abort_if_found)
register struct hblk *hbp;      /* ptr to current heap block            */
int abort_if_found;             /* Abort if a reclaimable object is found */
{
    hdr * hhdr;
    register word sz;           /* size of objects in current block     */
    register struct obj_kind * ok;
    register ptr_t * flh;
    
    hhdr = HDR(hbp);
    sz = hhdr -> hb_sz;
    ok = &GC_obj_kinds[hhdr -> hb_obj_kind];
    flh = &(ok -> ok_freelist[sz]);

    if (ok -> ok_init) {
      switch(sz) {
        case 2:
            *flh = GC_reclaim_clear2(hbp, hhdr, *flh, abort_if_found);
            break;
        case 4:
            *flh = GC_reclaim_clear4(hbp, hhdr, *flh, abort_if_found);
            break;
        default:
            *flh = GC_reclaim_clear(hbp, hhdr, sz, *flh, abort_if_found);
            break;
      }
    } else {
      switch(sz) {
        case 2:
            *flh = GC_reclaim_uninit2(hbp, hhdr, *flh, abort_if_found);
            break;
        case 4:
            *flh = GC_reclaim_uninit4(hbp, hhdr, *flh, abort_if_found);
            break;
        default:
            *flh = GC_reclaim_uninit(hbp, hhdr, sz, *flh, abort_if_found);
            break;
      }
    } 
}

/*
 * Restore an unmarked large object or an entirely empty blocks of small objects
 * to the heap block free list.
 * Otherwise enqueue the block for later processing
 * by GC_reclaim_small_nonempty_block.
 * If abort_if_found is TRUE, then process any block immediately.
 */
void GC_reclaim_block(hbp, abort_if_found)
register struct hblk *hbp;      /* ptr to current heap block            */
int abort_if_found;             /* Abort if a reclaimable object is found */
{
    register hdr * hhdr;
    register word sz;           /* size of objects in current block     */
    bool empty;                 /* used only for PRINTBLOCKS    */
    register struct obj_kind * ok;
    struct hblk ** rlh;

    hhdr = HDR(hbp);
    sz = hhdr -> hb_sz;
    ok = &GC_obj_kinds[hhdr -> hb_obj_kind];
#   ifdef PRINTBLOCKS
        GC_printf1("%ld(", (unsigned long)sz);
        if (hhdr -> hb_obj_kind == PTRFREE) {
            GC_printf0("a");
        } else if (hhdr -> hb_obj_kind == NORMAL){
            GC_printf0("c");
        } else {
            GC_printf0("o");
        }
#   endif

    if( sz > MAXOBJSZ ) {  /* 1 big object */
        if( mark_bit_from_hdr(hhdr, HDR_WORDS) ) {
            empty = FALSE;
        } else {
            FOUND_FREE(hbp, HDR_WORDS);
#           ifdef GATHERSTATS
                GC_mem_found += sz;
#           endif
            GC_freehblk(hbp);
            empty = TRUE;
        }
    } else {
        empty = GC_block_empty(hhdr);
        if (abort_if_found) {
          GC_reclaim_small_nonempty_block(hbp, abort_if_found);
        } else if (empty) {
#         ifdef GATHERSTATS
            GC_mem_found += BYTES_TO_WORDS(HBLKSIZE);
#         endif
          GC_freehblk(hbp);
        } else {
          /* group of smaller objects, enqueue the real work */
          rlh = &(ok -> ok_reclaim_list[sz]);
          hhdr -> hb_next = *rlh;
          *rlh = hbp;
        }
    }
#   ifdef PRINTBLOCKS
        if (empty) {GC_printf0("e),");} else {GC_printf0("n),");}
#   endif
}

/*
 * Do the same thing on the entire heap, after first clearing small object
 * free lists (if we are not just looking for leaks).
 */
void GC_start_reclaim(abort_if_found)
int abort_if_found;             /* Abort if a GC_reclaimable object is found */
{
    int kind;
    
    /* Clear reclaim- and free-lists */
      for (kind = 0; kind < GC_n_kinds; kind++) {
        register ptr_t *fop;
        register ptr_t *lim;
        register struct hblk ** hbpp;
        register struct hblk ** hlim;
          
        if (!abort_if_found) {
            lim = &(GC_obj_kinds[kind].ok_freelist[MAXOBJSZ+1]);
            for( fop = GC_obj_kinds[kind].ok_freelist; fop < lim; fop++ ) {
              *fop = 0;
            }
        } /* otherwise free list objects are marked,    */
          /* and its safe to leave them                 */
        hlim = &(GC_obj_kinds[kind].ok_reclaim_list[MAXOBJSZ+1]);
        for( hbpp = GC_obj_kinds[kind].ok_reclaim_list;
            hbpp < hlim; hbpp++ ) {
            *hbpp = 0;
        }
      }
    
#   ifdef PRINTBLOCKS
        GC_printf0("GC_reclaim: current block sizes:\n");
#   endif

  /* Go through all heap blocks (in hblklist) and reclaim unmarked objects */
  /* or enqueue the block for later processing.                            */
    GC_apply_to_all_blocks(GC_reclaim_block, abort_if_found);
    
#   ifdef PRINTBLOCKS
        GC_printf0("\n");
#   endif
}

/*
 * Sweep blocks of the indicated object size and kind until either the
 * appropriate free list is nonempty, or there are no more blocks to
 * sweep.
 */
void GC_continue_reclaim(sz, kind)
word sz;        /* words */
int kind;
{
    register hdr * hhdr;
    register struct hblk * hbp;
    register struct obj_kind * ok = &(GC_obj_kinds[kind]);
    struct hblk ** rlh = &(ok -> ok_reclaim_list[sz]);
    ptr_t *flh = &(ok -> ok_freelist[sz]);
    
    
    while ((hbp = *rlh) != 0) {
        hhdr = HDR(hbp);
        *rlh = hhdr -> hb_next;
        GC_reclaim_small_nonempty_block(hbp, FALSE);
        if (*flh != 0) break;
    }
}

---