1 /* 2 ** $Id: lgc.h $ 3 ** Garbage Collector 4 ** See Copyright Notice in lua.h 5 */ 6 7 #ifndef lgc_h 8 #define lgc_h 9 10 11 #include "lobject.h" 12 #include "lstate.h" 13 14 /* 15 ** Collectable objects may have one of three colors: white, which means 16 ** the object is not marked; gray, which means the object is marked, but 17 ** its references may be not marked; and black, which means that the 18 ** object and all its references are marked. The main invariant of the 19 ** garbage collector, while marking objects, is that a black object can 20 ** never point to a white one. Moreover, any gray object must be in a 21 ** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it 22 ** can be visited again before finishing the collection cycle. (Open 23 ** upvalues are an exception to this rule.) These lists have no meaning 24 ** when the invariant is not being enforced (e.g., sweep phase). 25 */ 26 27 28 /* 29 ** Possible states of the Garbage Collector 30 */ 31 #define GCSpropagate 0 32 #define GCSenteratomic 1 33 #define GCSatomic 2 34 #define GCSswpallgc 3 35 #define GCSswpfinobj 4 36 #define GCSswptobefnz 5 37 #define GCSswpend 6 38 #define GCScallfin 7 39 #define GCSpause 8 40 41 42 #define issweepphase(g) \ 43 (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend) 44 45 46 /* 47 ** macro to tell when main invariant (white objects cannot point to black 48 ** ones) must be kept. During a collection, the sweep 49 ** phase may break the invariant, as objects turned white may point to 50 ** still-black objects. The invariant is restored when sweep ends and 51 ** all objects are white again. 52 */ 53 54 #define keepinvariant(g) ((g)->gcstate <= GCSatomic) 55 56 57 /* 58 ** some useful bit tricks 59 */ 60 #define resetbits(x,m) ((x) &= cast_byte(~(m))) 61 #define setbits(x,m) ((x) |= (m)) 62 #define testbits(x,m) ((x) & (m)) 63 #define bitmask(b) (1<<(b)) 64 #define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2)) 65 #define l_setbit(x,b) setbits(x, bitmask(b)) 66 #define resetbit(x,b) resetbits(x, bitmask(b)) 67 #define testbit(x,b) testbits(x, bitmask(b)) 68 69 70 /* 71 ** Layout for bit use in 'marked' field. First three bits are 72 ** used for object "age" in generational mode. Last bit is used 73 ** by tests. 74 */ 75 #define WHITE0BIT 3 /* object is white (type 0) */ 76 #define WHITE1BIT 4 /* object is white (type 1) */ 77 #define BLACKBIT 5 /* object is black */ 78 #define FINALIZEDBIT 6 /* object has been marked for finalization */ 79 80 #define TESTBIT 7 81 82 83 84 #define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT) 85 86 87 #define iswhite(x) testbits((x)->marked, WHITEBITS) 88 #define isblack(x) testbit((x)->marked, BLACKBIT) 89 #define isgray(x) /* neither white nor black */ \ 90 (!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT))) 91 92 #define tofinalize(x) testbit((x)->marked, FINALIZEDBIT) 93 94 #define otherwhite(g) ((g)->currentwhite ^ WHITEBITS) 95 #define isdeadm(ow,m) ((m) & (ow)) 96 #define isdead(g,v) isdeadm(otherwhite(g), (v)->marked) 97 98 #define changewhite(x) ((x)->marked ^= WHITEBITS) 99 #define nw2black(x) \ 100 check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT)) 101 102 #define luaC_white(g) cast_byte((g)->currentwhite & WHITEBITS) 103 104 105 /* object age in generational mode */ 106 #define G_NEW 0 /* created in current cycle */ 107 #define G_SURVIVAL 1 /* created in previous cycle */ 108 #define G_OLD0 2 /* marked old by frw. barrier in this cycle */ 109 #define G_OLD1 3 /* first full cycle as old */ 110 #define G_OLD 4 /* really old object (not to be visited) */ 111 #define G_TOUCHED1 5 /* old object touched this cycle */ 112 #define G_TOUCHED2 6 /* old object touched in previous cycle */ 113 114 #define AGEBITS 7 /* all age bits (111) */ 115 116 #define getage(o) ((o)->marked & AGEBITS) 117 #define setage(o,a) ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a)) 118 #define isold(o) (getage(o) > G_SURVIVAL) 119 120 #define changeage(o,f,t) \ 121 check_exp(getage(o) == (f), (o)->marked ^= ((f)^(t))) 122 123 124 /* Default Values for GC parameters */ 125 #define LUAI_GENMAJORMUL 100 126 #define LUAI_GENMINORMUL 20 127 128 /* wait memory to double before starting new cycle */ 129 #define LUAI_GCPAUSE 200 130 131 /* 132 ** some gc parameters are stored divided by 4 to allow a maximum value 133 ** up to 1023 in a 'lu_byte'. 134 */ 135 #define getgcparam(p) ((p) * 4) 136 #define setgcparam(p,v) ((p) = (v) / 4) 137 138 #define LUAI_GCMUL 100 139 140 /* how much to allocate before next GC step (log2) */ 141 #define LUAI_GCSTEPSIZE 13 /* 8 KB */ 142 143 144 /* 145 ** Check whether the declared GC mode is generational. While in 146 ** generational mode, the collector can go temporarily to incremental 147 ** mode to improve performance. This is signaled by 'g->lastatomic != 0'. 148 */ 149 #define isdecGCmodegen(g) (g->gckind == KGC_GEN || g->lastatomic != 0) 150 151 /* 152 ** Does one step of collection when debt becomes positive. 'pre'/'pos' 153 ** allows some adjustments to be done only when needed. macro 154 ** 'condchangemem' is used only for heavy tests (forcing a full 155 ** GC cycle on every opportunity) 156 */ 157 #define luaC_condGC(L,pre,pos) \ 158 { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \ 159 condchangemem(L,pre,pos); } 160 161 /* more often than not, 'pre'/'pos' are empty */ 162 #define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0) 163 164 165 #define luaC_barrier(L,p,v) ( \ 166 (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \ 167 luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0)) 168 169 #define luaC_barrierback(L,p,v) ( \ 170 (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \ 171 luaC_barrierback_(L,p) : cast_void(0)) 172 173 #define luaC_objbarrier(L,p,o) ( \ 174 (isblack(p) && iswhite(o)) ? \ 175 luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0)) 176 177 LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o); 178 LUAI_FUNC void luaC_freeallobjects (lua_State *L); 179 LUAI_FUNC void luaC_step (lua_State *L); 180 LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask); 181 LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency); 182 LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz); 183 LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v); 184 LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o); 185 LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt); 186 LUAI_FUNC void luaC_changemode (lua_State *L, int newmode); 187 188 189 #endif 190