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some cleaning in 'sweeplist' (threads do not need to be traversed

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if they are going to be collected + use of bit masks to unify
differences in generational and incremental modes)
This commit is contained in:
Roberto Ierusalimschy 2010-05-06 15:18:07 -03:00
parent a4f20e3c8b
commit 25951e0ea5
1 changed files with 29 additions and 28 deletions
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57
lgc.c
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@ -1,5 +1,5 @@
/*
** $Id: lgc.c,v 2.88 2010/05/05 13:39:58 roberto Exp roberto $
** $Id: lgc.c,v 2.89 2010/05/05 18:58:36 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
@ -279,7 +279,6 @@ static void markmt (global_State *g) {
static void markbeingfnz (global_State *g) {
GCObject *o;
for (o = g->tobefnz; o != NULL; o = gch(o)->next) {
lua_assert(testbit(gch(o)->marked, SEPARATED));
makewhite(g, o);
reallymarkobject(g, o);
}
@ -293,7 +292,6 @@ static void markbeingfnz (global_State *g) {
static void remarkupvals (global_State *g) {
UpVal *uv;
for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
lua_assert(uv->u.l.next->u.l.prev == uv && uv->u.l.prev->u.l.next == uv);
if (isgray(obj2gco(uv)))
markvalue(g, uv->v);
}
@ -591,56 +589,59 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count);
** sweep the (open) upvalues of a thread and resize its stack and
** list of call-info structures.
*/
static void sweepthread (lua_State *L, lua_State *L1, int alive) {
static void sweepthread (lua_State *L, lua_State *L1) {
if (L1->stack == NULL) return; /* stack not completely built yet */
sweepwholelist(L, &L1->openupval); /* sweep open upvalues */
luaE_freeCI(L1); /* free extra CallInfo slots */
/* should not change the stack during an emergency gc cycle */
if (alive && G(L)->gckind != KGC_EMERGENCY)
if (G(L)->gckind != KGC_EMERGENCY)
luaD_shrinkstack(L1);
}
/*
** sweep a list of GCObjects, erasing dead objects, where a dead (not
** alive) object is one marked with the "old" (non current) white and
** not fixed.
** sweep at most 'count' elements from a list of GCObjects erasing dead
** objects, where a dead (not alive) object is one marked with the "old"
** (non current) white and not fixed.
** In non-generational mode, change all non-dead objects back to white,
** preparing for next collection cycle.
** In generational mode, keep black objects black, and also mark them
** as old; stop when hitting an old object, as all objects after that
** In generational mode, keep black objects black, and also mark them as
** old; stop when hitting an old object, as all objects after that
** one will be old too.
** When object is a thread, sweep its list of open upvalues too.
*/
static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
global_State *g = G(L);
int gckind = g->gckind;
int deadmask = otherwhite(g);
int white = luaC_white(g);
GCObject *curr;
while ((curr = *p) != NULL && count-- > 0) {
int toclear, toset; /* bits to clear and to set in all live objects */
if (g->gckind == KGC_GEN) { /* generational mode? */
toclear = ~0; /* clear nothing */
toset = OLDBIT; /* set the old bit of all surviving objects */
}
else { /* normal mode */
toclear = maskcolors; /* clear all color bits */
toset = luaC_white(g); /* make object white */
}
while (*p != NULL && count-- > 0) {
GCObject *curr = *p;
int marked = gch(curr)->marked;
int alive = (marked ^ WHITEBITS) & deadmask;
if (gch(curr)->tt == LUA_TTHREAD)
sweepthread(L, gco2th(curr), alive);
if (!alive) {
if (!((marked ^ WHITEBITS) & deadmask)) { /* is 'curr' dead? */
lua_assert(isdead(g, curr) || deadmask == 0);
*p = gch(curr)->next; /* remove 'curr' from list */
freeobj(L, curr); /* erase 'curr' */
}
else {
lua_assert(!isdead(g, curr) || testbit(marked, FIXEDBIT));
if (gckind == KGC_GEN) { /* generational mode? */
if (testbit(marked, OLDBIT)) { /* old generation? */
static GCObject *nullp = NULL;
return &nullp; /* stop sweeping this list */
}
else /* mark as old */
gch(curr)->marked = cast_byte(marked | bitmask(OLDBIT));
if (gch(curr)->tt == LUA_TTHREAD)
sweepthread(L, gco2th(curr)); /* sweep thread's upvalues */
if (testbit(marked, OLDBIT)) { /* old generation? */
static GCObject *nullp = NULL;
lua_assert(g->gckind == KGC_GEN); /* can happen only in gen. mode */
return &nullp; /* stop sweeping this list */
}
else /* not generational; makewhite */
gch(curr)->marked = cast_byte((marked & maskcolors) | white);
p = &gch(curr)->next;
/* update marks */
gch(curr)->marked = cast_byte((marked & toclear) | toset);
p = &gch(curr)->next; /* go to next element */
}
}
return p;