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| -rw-r--r-- | gc/doc/barrett_diagram | 106 |
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diff --git a/gc/doc/barrett_diagram b/gc/doc/barrett_diagram deleted file mode 100644 index 27e80dc..0000000 --- a/gc/doc/barrett_diagram +++ /dev/null @@ -1,106 +0,0 @@ -This is an ASCII diagram of the data structure used to check pointer -validity. It was provided by Dave Barrett <barrett@asgard.cs.colorado.edu>, -and should be of use to others attempting to understand the code. -The data structure in GC4.X is essentially the same. -HB - - - - - Data Structure used by GC_base in gc3.7: - 21-Apr-94 - - - - - 63 LOG_TOP_SZ[11] LOG_BOTTOM_SZ[10] LOG_HBLKSIZE[13] - +------------------+----------------+------------------+------------------+ - p:| | TL_HASH(hi) | | HBLKDISPL(p) | - +------------------+----------------+------------------+------------------+ - \-----------------------HBLKPTR(p)-------------------/ - \------------hi-------------------/ - \______ ________/ \________ _______/ \________ _______/ - V V V - | | | - GC_top_index[] | | | - --- +--------------+ | | | - ^ | | | | | - | | | | | | - TOP +--------------+<--+ | | - _SZ +-<| [] | * | | -(items)| +--------------+ if 0 < bi< HBLKSIZE | | - | | | | then large object | | - | | | | starts at the bi'th | | - v | | | HBLK before p. | i | - --- | +--------------+ | (word- | - v | aligned) | - bi= |GET_BI(p){->hash_link}->key==hi | | - v | | - | (bottom_index) \ scratch_alloc'd | | - | ( struct bi ) / by get_index() | | - --- +->+--------------+ | | - ^ | | | | - ^ | | | | - BOTTOM | | ha=GET_HDR_ADDR(p) | | -_SZ(items)+--------------+<----------------------+ +-------+ - | +--<| index[] | | - | | +--------------+ GC_obj_map: v - | | | | from / +-+-+-----+-+-+-+-+ --- - v | | | GC_add < 0| | | | | | | | ^ - --- | +--------------+ _map_entry \ +-+-+-----+-+-+-+-+ | - | | asc_link | +-+-+-----+-+-+-+-+ MAXOBJSZ - | +--------------+ +-->| | | j | | | | | +1 - | | key | | +-+-+-----+-+-+-+-+ | - | +--------------+ | +-+-+-----+-+-+-+-+ | - | | hash_link | | | | | | | | | | v - | +--------------+ | +-+-+-----+-+-+-+-+ --- - | | |<--MAX_OFFSET--->| - | | (bytes) -HDR(p)| GC_find_header(p) | |<--MAP_ENTRIES-->| - | \ from | =HBLKSIZE/WORDSZ - | (hdr) (struct hblkhdr) / alloc_hdr() | (1024 on Alpha) - +-->+----------------------+ | (8/16 bits each) -GET_HDR(p)| word hb_sz (words) | | - +----------------------+ | - | struct hblk *hb_next | | - +----------------------+ | - |mark_proc hb_mark_proc| | - +----------------------+ | - | char * hb_map |>-------------+ - +----------------------+ - | ushort hb_obj_kind | - +----------------------+ - | hb_last_reclaimed | - --- +----------------------+ - ^ | | - MARK_BITS| hb_marks[] | *if hdr is free, hb_sz + DISCARD_WORDS -_SZ(words)| | is the size of a heap chunk (struct hblk) - v | | of at least MININCR*HBLKSIZE bytes (below), - --- +----------------------+ otherwise, size of each object in chunk. - -Dynamic data structures above are interleaved throughout the heap in blocks of -size MININCR * HBLKSIZE bytes as done by gc_scratch_alloc which cannot be -freed; free lists are used (e.g. alloc_hdr). HBLKs's below are collected. - - (struct hblk) - --- +----------------------+ < HBLKSIZE --- --- DISCARD_ - ^ |garbage[DISCARD_WORDS]| aligned ^ ^ HDR_BYTES WORDS - | | | | v (bytes) (words) - | +-----hb_body----------+ < WORDSZ | --- --- - | | | aligned | ^ ^ - | | Object 0 | | hb_sz | - | | | i |(word- (words)| - | | | (bytes)|aligned) v | - | + - - - - - - - - - - -+ --- | --- | - | | | ^ | ^ | - n * | | j (words) | hb_sz BODY_SZ - HBLKSIZE | Object 1 | v v | (words) - (bytes) | |--------------- v MAX_OFFSET - | + - - - - - - - - - - -+ --- (bytes) - | | | !All_INTERIOR_PTRS ^ | - | | | sets j only for hb_sz | - | | Object N | valid object offsets. | | - v | | All objects WORDSZ v v - --- +----------------------+ aligned. --- --- - -DISCARD_WORDS is normally zero. Indeed the collector has not been tested -with another value in ages. |