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do not try to ensure that 'sweepgc' points to a live object 

when entering sweep phase ('entersweep'); that may be too
expensive to be done still inside the atomic step. Walking
one single object more often than not will work.
This commit is contained in:
Roberto Ierusalimschy 2016-03-31 16:02:03 -03:00
parent d77a7a8c26
commit 8d4feb504f
1 changed files with 11 additions and 18 deletions
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29
lgc.c
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@ -1,5 +1,5 @@
/*
** $Id: lgc.c,v 2.210 2015/11/03 18:10:44 roberto Exp roberto $
** $Id: lgc.c,v 2.211 2015/12/10 18:12:30 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
@ -754,14 +754,11 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
/*
** sweep a list until a live object (or end of list)
*/
static GCObject **sweeptolive (lua_State *L, GCObject **p, int *n) {
static GCObject **sweeptolive (lua_State *L, GCObject **p) {
GCObject **old = p;
int i = 0;
do {
i++;
p = sweeplist(L, p, 1);
} while (p == old);
if (n) *n += i;
return p;
}
@ -909,7 +906,7 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
if (issweepphase(g)) {
makewhite(g, o); /* "sweep" object 'o' */
if (g->sweepgc == &o->next) /* should not remove 'sweepgc' object */
g->sweepgc = sweeptolive(L, g->sweepgc, NULL); /* change 'sweepgc' */
g->sweepgc = sweeptolive(L, g->sweepgc); /* change 'sweepgc' */
}
/* search for pointer pointing to 'o' */
for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ }
@ -951,19 +948,16 @@ static void setpause (global_State *g) {
/*
** Enter first sweep phase.
** The call to 'sweeptolive' makes pointer point to an object inside
** the list (instead of to the header), so that the real sweep do not
** need to skip objects created between "now" and the start of the real
** sweep.
** Returns how many objects it swept.
** The call to 'sweeplist' tries to make pointer point to an object
** inside the list (instead of to the header), so that the real sweep do
** not need to skip objects created between "now" and the start of the
** real sweep.
*/
static int entersweep (lua_State *L) {
static void entersweep (lua_State *L) {
global_State *g = G(L);
int n = 0;
g->gcstate = GCSswpallgc;
lua_assert(g->sweepgc == NULL);
g->sweepgc = sweeptolive(L, &g->allgc, &n);
return n;
g->sweepgc = sweeplist(L, &g->allgc, 1);
}
@ -1064,12 +1058,11 @@ static lu_mem singlestep (lua_State *L) {
}
case GCSatomic: {
lu_mem work;
int sw;
propagateall(g); /* make sure gray list is empty */
work = atomic(L); /* work is what was traversed by 'atomic' */
sw = entersweep(L);
entersweep(L);
g->GCestimate = gettotalbytes(g); /* first estimate */;
return work + sw * GCSWEEPCOST;
return work;
}
case GCSswpallgc: { /* sweep "regular" objects */
return sweepstep(L, g, GCSswpfinobj, &g->finobj);