/* ** $Id: lgc.h $ ** Garbage Collector ** See Copyright Notice in lua.h */ #ifndef lgc_h #define lgc_h #include #include "lobject.h" #include "lstate.h" /* ** Collectable objects may have one of three colors: white, which means ** the object is not marked; gray, which means the object is marked, but ** its references may be not marked; and black, which means that the ** object and all its references are marked. The main invariant of the ** garbage collector, while marking objects, is that a black object can ** never point to a white one. Moreover, any gray object must be in a ** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it ** can be visited again before finishing the collection cycle. (Open ** upvalues are an exception to this rule.) These lists have no meaning ** when the invariant is not being enforced (e.g., sweep phase). */ /* ** Possible states of the Garbage Collector */ #define GCSpropagate 0 #define GCSenteratomic 1 #define GCSatomic 2 #define GCSswpallgc 3 #define GCSswpfinobj 4 #define GCSswptobefnz 5 #define GCSswpend 6 #define GCScallfin 7 #define GCSpause 8 #define issweepphase(g) \ (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend) /* ** macro to tell when main invariant (white objects cannot point to black ** ones) must be kept. During a collection, the sweep ** phase may break the invariant, as objects turned white may point to ** still-black objects. The invariant is restored when sweep ends and ** all objects are white again. */ #define keepinvariant(g) ((g)->gcstate <= GCSatomic) /* ** some useful bit tricks */ #define resetbits(x,m) ((x) &= cast_byte(~(m))) #define setbits(x,m) ((x) |= (m)) #define testbits(x,m) ((x) & (m)) #define bitmask(b) (1<<(b)) #define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2)) #define l_setbit(x,b) setbits(x, bitmask(b)) #define resetbit(x,b) resetbits(x, bitmask(b)) #define testbit(x,b) testbits(x, bitmask(b)) /* ** Layout for bit use in 'marked' field. First three bits are ** used for object "age" in generational mode. Last bit is used ** by tests. */ #define WHITE0BIT 3 /* object is white (type 0) */ #define WHITE1BIT 4 /* object is white (type 1) */ #define BLACKBIT 5 /* object is black */ #define FINALIZEDBIT 6 /* object has been marked for finalization */ #define TESTBIT 7 #define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT) #define iswhite(x) testbits((x)->marked, WHITEBITS) #define isblack(x) testbit((x)->marked, BLACKBIT) #define isgray(x) /* neither white nor black */ \ (!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT))) #define tofinalize(x) testbit((x)->marked, FINALIZEDBIT) #define otherwhite(g) ((g)->currentwhite ^ WHITEBITS) #define isdeadm(ow,m) ((m) & (ow)) #define isdead(g,v) isdeadm(otherwhite(g), (v)->marked) #define changewhite(x) ((x)->marked ^= WHITEBITS) #define nw2black(x) \ check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT)) #define luaC_white(g) cast_byte((g)->currentwhite & WHITEBITS) /* object age in generational mode */ #define G_NEW 0 /* created in current cycle */ #define G_SURVIVAL 1 /* created in previous cycle */ #define G_OLD0 2 /* marked old by frw. barrier in this cycle */ #define G_OLD1 3 /* first full cycle as old */ #define G_OLD 4 /* really old object (not to be visited) */ #define G_TOUCHED1 5 /* old object touched this cycle */ #define G_TOUCHED2 6 /* old object touched in previous cycle */ #define AGEBITS 7 /* all age bits (111) */ #define getage(o) ((o)->marked & AGEBITS) #define setage(o,a) ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a)) #define isold(o) (getage(o) > G_SURVIVAL) #define changeage(o,f,t) \ check_exp(getage(o) == (f), (o)->marked ^= ((f)^(t))) /* Default Values for GC parameters */ /* generational */ #define LUAI_GENMAJORMUL 100 /* major multiplier */ #define LUAI_GENMINORMUL 20 /* minor multiplier */ /* incremental */ /* wait memory to double before starting new cycle */ #define LUAI_GCPAUSE 200 #define LUAI_GCMUL 300 /* step multiplier */ /* how many objects to allocate before next GC step (log2) */ #define LUAI_GCSTEPSIZE 8 /* 256 objects */ /* ** Control when GC is running: */ #define GCSTPUSR 1 /* bit true when GC stopped by user */ #define GCSTPGC 2 /* bit true when GC stopped by itself */ #define GCSTPCLS 4 /* bit true when closing Lua state */ #define gcrunning(g) ((g)->gcstp == 0) /* ** Macros to set and apply GC parameters. GC parameters are given in ** percentage points, but are stored as lu_byte. To reduce their ** values and avoid repeated divisions by 100, these macros store ** the original parameter multiplied by 2^n and divided by 100. ** To apply them, the value is divided by 2^n (a shift) and then ** multiplied by the stored parameter, yielding ** value / 2^n * (original parameter * 2^n / 100), or approximately ** (value * original parameter / 100). ** ** For most parameters, which are typically larger than 100%, 2^n is ** 16 (2^4), allowing maximum values up to 1599. For the minor ** multiplier, which is typically smaller, 2^n is 64 (2^6) to allow more ** precision. */ #define gcparamshift(p) \ (offsetof(global_State, p) == offsetof(global_State, genminormul) ? 6 : 4) #define setgcparam(g,p,v) \ (g->p = (cast_uint(v) << gcparamshift(p)) / 100u) #define applygcparam(g,p,v) (((v) >> gcparamshift(p)) * g->p) /* ** Does one step of collection when debt becomes zero. 'pre'/'pos' ** allows some adjustments to be done only when needed. macro ** 'condchangemem' is used only for heavy tests (forcing a full ** GC cycle on every opportunity) */ #define luaC_condGC(L,pre,pos) \ { if (G(L)->GCdebt <= 0) { pre; luaC_step(L); pos;}; \ condchangemem(L,pre,pos); } /* more often than not, 'pre'/'pos' are empty */ #define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0) #define luaC_objbarrier(L,p,o) ( \ (isblack(p) && iswhite(o)) ? \ luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0)) #define luaC_barrier(L,p,v) ( \ iscollectable(v) ? luaC_objbarrier(L,p,gcvalue(v)) : cast_void(0)) #define luaC_objbarrierback(L,p,o) ( \ (isblack(p) && iswhite(o)) ? luaC_barrierback_(L,p) : cast_void(0)) #define luaC_barrierback(L,p,v) ( \ iscollectable(v) ? luaC_objbarrierback(L, p, gcvalue(v)) : cast_void(0)) LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o); LUAI_FUNC void luaC_freeallobjects (lua_State *L); LUAI_FUNC void luaC_step (lua_State *L); LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask); LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency); LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz); LUAI_FUNC GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz, size_t offset); LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v); LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o); LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt); LUAI_FUNC void luaC_changemode (lua_State *L, int newmode); #endif