reclaim.c

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/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1996 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
 * Copyright (c) 1999 by Hewlett-Packard Company. 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 use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */

#include <stdio.h>
#include "private/gc_priv.h"

signed_word GC_mem_found = 0;
			/* Number of words of memory reclaimed     */

#if defined(PARALLEL_MARK) || defined(THREAD_LOCAL_ALLOC)
  word GC_fl_builder_count = 0;
	/* Number of threads currently building free lists without 	*/
	/* holding GC lock.  It is not safe to collect if this is 	*/
	/* nonzero.							*/
#endif /* PARALLEL_MARK */

/* We defer printing of leaked objects until we're done with the GC	*/
/* cycle, since the routine for printing objects needs to run outside	*/
/* the collector, e.g. without the allocation lock.			*/
#define MAX_LEAKED 40
ptr_t GC_leaked[MAX_LEAKED];
unsigned GC_n_leaked = 0;

GC_bool GC_have_errors = FALSE;

void GC_add_leaked(leaked)
ptr_t leaked;
{
    if (GC_n_leaked < MAX_LEAKED) {
      GC_have_errors = TRUE;
      GC_leaked[GC_n_leaked++] = leaked;
      /* Make sure it's not reclaimed this cycle */
        GC_set_mark_bit(leaked);
    }
}

static GC_bool printing_errors = FALSE;
/* Print all objects on the list after printing any smashed objs. 	*/
/* Clear both lists.							*/
void GC_print_all_errors ()
{
    unsigned i;

    LOCK();
    if (printing_errors) {
	UNLOCK();
	return;
    }
    printing_errors = TRUE;
    UNLOCK();
    if (GC_debugging_started) GC_print_all_smashed();
    for (i = 0; i < GC_n_leaked; ++i) {
	ptr_t p = GC_leaked[i];
	if (HDR(p) -> hb_obj_kind == PTRFREE) {
	    GC_err_printf0("Leaked atomic object at ");
	} else {
	    GC_err_printf0("Leaked composite object at ");
	}
	GC_print_heap_obj(p);
	GC_err_printf0("\n");
	GC_free(p);
	GC_leaked[i] = 0;
    }
    GC_n_leaked = 0;
    printing_errors = FALSE;
}


#   define FOUND_FREE(hblk, word_no) \
      { \
         GC_add_leaked((ptr_t)hblk + WORDS_TO_BYTES(word_no)); \
      }

/*
 * 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.
 */
 
GC_bool GC_block_empty(hhdr)
register hdr * hhdr;
{
    /* We treat hb_marks as an array of words here, even if it is 	*/
    /* actually an array of bytes.  Since we only check for zero, there	*/
    /* are no endian-ness issues.					*/
    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);
}

/* The following functions sometimes return a DONT_KNOW value. */
#define DONT_KNOW  2

#ifdef SMALL_CONFIG
# define GC_block_nearly_full1(hhdr, pat1) DONT_KNOW
# define GC_block_nearly_full3(hhdr, pat1, pat2) DONT_KNOW
# define GC_block_nearly_full(hhdr) DONT_KNOW
#endif

#if !defined(SMALL_CONFIG) && defined(USE_MARK_BYTES)

# define GC_block_nearly_full1(hhdr, pat1) GC_block_nearly_full(hhdr)
# define GC_block_nearly_full3(hhdr, pat1, pat2) GC_block_nearly_full(hhdr)

 
GC_bool GC_block_nearly_full(hhdr)
register hdr * hhdr;
{
    /* We again treat hb_marks as an array of words, even though it	*/
    /* isn't.  We first sum up all the words, resulting in a word 	*/
    /* containing 4 or 8 separate partial sums. 			*/
    /* We then sum the bytes in the word of partial sums.		*/
    /* This is still endian independant.  This fails if the partial	*/
    /* sums can overflow.						*/
#   if (BYTES_TO_WORDS(MARK_BITS_SZ)) >= 256
	--> potential overflow; fix the code
#   endif
    register word *p = (word *)(&(hhdr -> hb_marks[0]));
    register word * plim =
	    (word *)(&(hhdr -> hb_marks[MARK_BITS_SZ]));
    word sum_vector = 0;
    unsigned sum;
    while (p < plim) {
	sum_vector += *p;
	++p;
    }
    sum = 0;
    while (sum_vector > 0) {
	sum += sum_vector & 0xff;
	sum_vector >>= 8;
    }
    return (sum > BYTES_TO_WORDS(7*HBLKSIZE/8)/(hhdr -> hb_sz));
}
#endif  /* USE_MARK_BYTES */

#if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES)

/*
 * Test whether nearly all of the mark words consist of the same
 * repeating pattern.
 */
#define FULL_THRESHOLD (MARK_BITS_SZ/16)

GC_bool GC_block_nearly_full1(hhdr, pat1)
hdr *hhdr;
word pat1;
{
    unsigned i;
    unsigned misses = 0;
    GC_ASSERT((MARK_BITS_SZ & 1) == 0);
    for (i = 0; i < MARK_BITS_SZ; ++i) {
	if ((hhdr -> hb_marks[i] | ~pat1) != ONES) {
	    if (++misses > FULL_THRESHOLD) return FALSE;
	}
    }
    return TRUE;
}

/*
 * Test whether the same repeating 3 word pattern occurs in nearly
 * all the mark bit slots.
 * This is used as a heuristic, so we're a bit sloppy and ignore
 * the last one or two words.
 */
GC_bool GC_block_nearly_full3(hhdr, pat1, pat2, pat3)
hdr *hhdr;
word pat1, pat2, pat3;
{
    unsigned i;
    unsigned misses = 0;

    if (MARK_BITS_SZ < 4) {
      return DONT_KNOW;
    }
    for (i = 0; i < MARK_BITS_SZ - 2; i += 3) {
	if ((hhdr -> hb_marks[i] | ~pat1) != ONES) {
	    if (++misses > FULL_THRESHOLD) return FALSE;
	}
	if ((hhdr -> hb_marks[i+1] | ~pat2) != ONES) {
	    if (++misses > FULL_THRESHOLD) return FALSE;
	}
	if ((hhdr -> hb_marks[i+2] | ~pat3) != ONES) {
	    if (++misses > FULL_THRESHOLD) return FALSE;
	}
    }
    return TRUE;
}

/* Check whether a small object block is nearly full by looking at only */
/* the mark bits.							*/
/* We manually precomputed the mark bit patterns that need to be 	*/
/* checked for, and we give up on the ones that are unlikely to occur,	*/
/* or have period > 3.							*/
/* This would be a lot easier with a mark bit per object instead of per	*/
/* word, but that would rewuire computing object numbers in the mark	*/
/* loop, which would require different data structures ...		*/
GC_bool GC_block_nearly_full(hhdr)
hdr *hhdr;
{
    int sz = hhdr -> hb_sz;

#   if CPP_WORDSZ != 32 && CPP_WORDSZ != 64
      return DONT_KNOW;	/* Shouldn't be used in any standard config.	*/
#   endif
#   if CPP_WORDSZ == 32
      switch(sz) {
        case 1:
	  return GC_block_nearly_full1(hhdr, 0xffffffffl);
	case 2:
	  return GC_block_nearly_full1(hhdr, 0x55555555l);
	case 4:
	  return GC_block_nearly_full1(hhdr, 0x11111111l);
	case 6:
	  return GC_block_nearly_full3(hhdr, 0x41041041l,
					      0x10410410l,
					       0x04104104l);
	case 8:
	  return GC_block_nearly_full1(hhdr, 0x01010101l);
	case 12:
	  return GC_block_nearly_full3(hhdr, 0x01001001l,
					      0x10010010l,
					       0x00100100l);
	case 16:
	  return GC_block_nearly_full1(hhdr, 0x00010001l);
	case 32:
	  return GC_block_nearly_full1(hhdr, 0x00000001l);
	default:
	  return DONT_KNOW;
      }
#   endif
#   if CPP_WORDSZ == 64
      switch(sz) {
        case 1:
	  return GC_block_nearly_full1(hhdr, 0xffffffffffffffffl);
	case 2:
	  return GC_block_nearly_full1(hhdr, 0x5555555555555555l);
	case 4:
	  return GC_block_nearly_full1(hhdr, 0x1111111111111111l);
	case 6:
	  return GC_block_nearly_full3(hhdr, 0x1041041041041041l,
					       0x4104104104104104l,
					         0x0410410410410410l);
	case 8:
	  return GC_block_nearly_full1(hhdr, 0x0101010101010101l);
	case 12:
	  return GC_block_nearly_full3(hhdr, 0x1001001001001001l,
					       0x0100100100100100l,
					         0x0010010010010010l);
	case 16:
	  return GC_block_nearly_full1(hhdr, 0x0001000100010001l);
	case 32:
	  return GC_block_nearly_full1(hhdr, 0x0000000100000001l);
	default:
	  return DONT_KNOW;
      }
#   endif
}
#endif /* !SMALL_CONFIG  && !USE_MARK_BYTES */

/* We keep track of reclaimed memory if we are either asked to, or	*/
/* we are using the parallel marker.  In the latter case, we assume	*/
/* that most allocation goes through GC_malloc_many for scalability.	*/
/* GC_malloc_many needs the count anyway.				*/
# if defined(GATHERSTATS) || defined(PARALLEL_MARK)
#   define INCR_WORDS(sz) n_words_found += (sz)
#   define COUNT_PARAM , count
#   define COUNT_ARG , count
#   define COUNT_DECL signed_word * count;
#   define NWORDS_DECL signed_word n_words_found = 0;
#   define COUNT_UPDATE *count += n_words_found;
#   define MEM_FOUND_ADDR , &GC_mem_found
# else
#   define INCR_WORDS(sz)
#   define COUNT_PARAM
#   define COUNT_ARG
#   define COUNT_DECL
#   define NWORDS_DECL
#   define COUNT_UPDATE
#   define MEM_FOUND_ADDR
# 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 COUNT_PARAM)
register struct hblk *hbp;	/* ptr to current heap block		*/
register hdr * hhdr;
register ptr_t list;
register word sz;
COUNT_DECL
{
    register int word_no;
    register word *p, *q, *plim;
    NWORDS_DECL
    
    GC_ASSERT(hhdr == GC_find_header((ptr_t)hbp));
    p = (word *)(hbp->hb_body);
    word_no = 0;
    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 {
		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;
#		    ifdef USE_MARK_BYTES
		      GC_ASSERT(!(sz & 1)
				&& !((word)p & (2 * sizeof(word) - 1)));
		      p[1] = 0;
                      p += 2;
                      while (p < q) {
			CLEAR_DOUBLE(p);
			p += 2;
		      }
#		    else
                      p++; /* Skip link field */
                      while (p < q) {
			*p++ = 0;
		      }
#		    endif
	    }
	    word_no += sz;
	}
    COUNT_UPDATE
    return(list);
}

#if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES)

/*
 * A special case for 2 word composite objects (e.g. cons cells):
 */
/*ARGSUSED*/
ptr_t GC_reclaim_clear2(hbp, hhdr, list COUNT_PARAM)
register struct hblk *hbp;	/* ptr to current heap block		*/
hdr * hhdr;
register ptr_t list;
COUNT_DECL
{
    register word * mark_word_addr = &(hhdr->hb_marks[0]);
    register word *p, *plim;
    register word mark_word;
    register int i;
    NWORDS_DECL
#   define DO_OBJ(start_displ) \
	if (!(mark_word & ((word)1 << 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 *)(((word)hbp) + HBLKSIZE);

    /* go through all words in block */
	while( p < plim )  {
	    mark_word = *mark_word_addr++;
	    for (i = 0; i < WORDSZ; i += 8) {
		DO_OBJ(0);
		DO_OBJ(2);
		DO_OBJ(4);
		DO_OBJ(6);
		p += 8;
		mark_word >>= 8;
	    }
	}	        
    COUNT_UPDATE
    return(list);
#   undef DO_OBJ
}

/*
 * Another special case for 4 word composite objects:
 */
/*ARGSUSED*/
ptr_t GC_reclaim_clear4(hbp, hhdr, list COUNT_PARAM)
register struct hblk *hbp;	/* ptr to current heap block		*/
hdr * hhdr;
register ptr_t list;
COUNT_DECL
{
    register word * mark_word_addr = &(hhdr->hb_marks[0]);
    register word *p, *plim;
    register word mark_word;
    NWORDS_DECL
#   define DO_OBJ(start_displ) \
	if (!(mark_word & ((word)1 << start_displ))) { \
	    p[start_displ] = (word)list; \
	    list = (ptr_t)(p+start_displ); \
	    p[start_displ+1] = 0; \
	    CLEAR_DOUBLE(p + start_displ + 2); \
	    INCR_WORDS(4); \
	}
    
    p = (word *)(hbp->hb_body);
    plim = (word *)(((word)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);
#	    if CPP_WORDSZ == 64
	      DO_OBJ(32);
	      DO_OBJ(36);
	      DO_OBJ(40);
	      DO_OBJ(44);
	      DO_OBJ(48);
	      DO_OBJ(52);
	      DO_OBJ(56);
	      DO_OBJ(60);
#	    endif
	    p += WORDSZ;
	}	        
    COUNT_UPDATE
    return(list);
#   undef DO_OBJ
}

#endif /* !SMALL_CONFIG && !USE_MARK_BYTES */

/* The same thing, but don't clear objects: */
/*ARGSUSED*/
ptr_t GC_reclaim_uninit(hbp, hhdr, sz, list COUNT_PARAM)
register struct hblk *hbp;	/* ptr to current heap block		*/
register hdr * hhdr;
register ptr_t list;
register word sz;
COUNT_DECL
{
    register int word_no = 0;
    register word *p, *plim;
    NWORDS_DECL
    
    p = (word *)(hbp->hb_body);
    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) ) {
		INCR_WORDS(sz);
		/* object is available - put on list */
		    obj_link(p) = list;
		    list = ((ptr_t)p);
	    }
	    p += sz;
	    word_no += sz;
	}
    COUNT_UPDATE
    return(list);
}

/* Don't really reclaim objects, just check for unmarked ones: */
/*ARGSUSED*/
void GC_reclaim_check(hbp, hhdr, sz)
register struct hblk *hbp;	/* ptr to current heap block		*/
register hdr * hhdr;
register word sz;
{
    register int word_no = 0;
    register word *p, *plim;
#   ifdef GATHERSTATS
        register int n_words_found = 0;
#   endif
    
    p = (word *)(hbp->hb_body);
    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) ) {
		FOUND_FREE(hbp, word_no);
	    }
	    p += sz;
	    word_no += sz;
	}
}

#if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES)
/*
 * Another special case for 2 word atomic objects:
 */
/*ARGSUSED*/
ptr_t GC_reclaim_uninit2(hbp, hhdr, list COUNT_PARAM)
register struct hblk *hbp;	/* ptr to current heap block		*/
hdr * hhdr;
register ptr_t list;
COUNT_DECL
{
    register word * mark_word_addr = &(hhdr->hb_marks[0]);