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generational mode no longer sweep old objects

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This commit is contained in:
Roberto Ierusalimschy 2010-03-24 12:51:10 -03:00
parent 4433dbb5f5
commit 64d39ed1b6
2 changed files with 41 additions and 19 deletions
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56
lgc.c
View File

@ -1,5 +1,5 @@
/*
** $Id: lgc.c,v 2.69 2010/03/23 20:16:06 roberto Exp roberto $
** $Id: lgc.c,v 2.70 2010/03/24 13:07:01 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
@ -31,12 +31,13 @@
#define GCATOMICCOST 1000
#define maskcolors (~(bitmask(BLACKBIT)|WHITEBITS))
#define makewhitew(w,x) \
(gch(x)->marked = cast_byte((gch(x)->marked & maskcolors) | (w)))
#define makewhite(g,x) makewhitew(luaC_white(g), x)
/*
** 'makewhite' erases all color bits plus the old bit and then
** sets only the current white bit
*/
#define maskcolors (~(bit2mask(BLACKBIT, OLDBIT) | WHITEBITS))
#define makewhite(w,x) \
(gch(x)->marked = cast_byte((gch(x)->marked & maskcolors) | luaC_white(g)))
#define white2gray(x) resetbits(gch(x)->marked, WHITEBITS)
#define black2gray(x) resetbit(gch(x)->marked, BLACKBIT)
@ -548,27 +549,46 @@ static void sweepthread (lua_State *L, lua_State *L1, int alive) {
}
/*
** 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.
** 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
** 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) {
GCObject *curr;
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 alive = (gch(curr)->marked ^ WHITEBITS) & deadmask;
int marked = gch(curr)->marked;
int alive = (marked ^ WHITEBITS) & deadmask;
if (gch(curr)->tt == LUA_TTHREAD)
sweepthread(L, gco2th(curr), alive);
if (alive) {
lua_assert(!isdead(g, curr) || testbit(gch(curr)->marked, FIXEDBIT));
/* in generational mode all live objects are kept black, which
means they grow to old generation */
if (gckind != KGC_GEN) makewhitew(white, curr);
p = &gch(curr)->next;
}
else { /* must erase `curr' */
if (!alive) {
lua_assert(isdead(g, curr) || deadmask == bitmask(SFIXEDBIT));
*p = gch(curr)->next; /* remove 'curr' from list */
freeobj(L, curr);
freeobj(L, curr); /* erase 'curr' */
}
else {
lua_assert(!isdead(g, curr) || testbit(gch(curr)->marked, FIXEDBIT));
if (gckind == KGC_GEN) { /* generational mode? */
if (testbit(gch(curr)->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));
}
else /* not generational; makewhite */
gch(curr)->marked = cast_byte((marked & maskcolors) | white);
p = &gch(curr)->next;
}
}
return p;

4
lgc.h
View File

@ -1,5 +1,5 @@
/*
** $Id: lgc.h,v 2.27 2009/12/16 16:42:58 roberto Exp roberto $
** $Id: lgc.h,v 2.28 2010/03/24 13:07:01 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
@ -49,6 +49,7 @@
** bit 4 - for userdata: it's in 'udgc' list or in 'tobefnz'
** bit 5 - object is fixed (should not be collected)
** bit 6 - object is "super" fixed (only the main thread)
** bit 7 - object is old (only in generational mode)
*/
#define WHITE0BIT 0
#define WHITE1BIT 1
@ -57,6 +58,7 @@
#define SEPARATED 4
#define FIXEDBIT 5
#define SFIXEDBIT 6
#define OLDBIT 7
#define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT)