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Simplification in handling of GC debt

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Each incremental step has always the same size (stepsize), and the
debt for next step also is always the same.
This commit is contained in:
Roberto Ierusalimschy 2022-12-06 12:02:34 -03:00
parent efc7c5d503
commit 0270c204c2
2 changed files with 22 additions and 20 deletions
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30
lapi.c
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@ -1145,7 +1145,7 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
}
case LUA_GCRESTART: {
luaE_setdebt(g, 0);
g->gcstp = 0; /* (GCSTPGC must be already zero here) */
g->gcstp = 0; /* (bit GCSTPGC must be zero here) */
break;
}
case LUA_GCCOLLECT: {
@ -1162,21 +1162,25 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
break;
}
case LUA_GCSTEP: {
int data = va_arg(argp, int);
l_obj debt = 1; /* =1 to signal that it did an actual step */
int todo = va_arg(argp, int); /* work to be done */
int didsomething = 0;
lu_byte oldstp = g->gcstp;
g->gcstp = 0; /* allow GC to run (GCSTPGC must be zero here) */
if (data == 0) {
luaE_setdebt(g, 0); /* do a basic step */
luaC_step(L);
}
else { /* add 'data' to total debt */
debt = data + g->GCdebt;
luaE_setdebt(g, debt);
luaC_checkGC(L);
g->gcstp = 0; /* allow GC to run (bit GCSTPGC must be zero here) */
if (todo == 0)
todo = 1 << g->gcstepsize; /* standard step size */
while (todo + g->GCdebt > 0) { /* enough to run a step? */
todo += g->GCdebt; /* decrement 'todo' (debt is usually negative) */
luaC_step(L); /* run one basic step */
didsomething = 1;
if (g->gckind == KGC_GEN) /* minor collections? */
todo = 0; /* doesn't make sense to repeat in this case */
else if (g->gcstate == GCSpause)
break; /* don't run more than one cycle */
}
/* add remaining 'todo' to total debt */
luaE_setdebt(g, todo + g->GCdebt);
g->gcstp = oldstp; /* restore previous state */
if (debt > 0 && g->gcstate == GCSpause) /* end of cycle? */
if (didsomething && g->gcstate == GCSpause) /* end of cycle? */
res = 1; /* signal it */
break;
}

12
lgc.c
View File

@ -1037,7 +1037,7 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
*/
static void setpause (global_State *g) {
unsigned int pause = getgcparam(g->gcpause);
lu_mem threshold = g->marked / 8 * pause / 12;
l_obj threshold = g->marked / 8 * pause / 12;
l_obj debt = gettotalobjs(g) - threshold;
if (debt > 0) debt = 0;
luaE_setdebt(g, debt);
@ -1600,18 +1600,16 @@ void luaC_runtilstate (lua_State *L, int statesmask) {
** controls when next step will be performed.
*/
static void incstep (lua_State *L, global_State *g) {
int stepmul = (getgcparam(g->gcstepmul) | 1); /* avoid division by 0 */
l_obj debt = (g->GCdebt / 100) * stepmul;
l_obj stepsize = cast(l_obj, 1) << g->gcstepsize;
l_obj work2do = stepsize * getgcparam(g->gcstepmul) / 100;
do { /* repeat until pause or enough "credit" (negative debt) */
l_obj work = singlestep(L); /* perform one single step */
debt -= work;
} while (debt > -stepsize && g->gcstate != GCSpause);
work2do -= work;
} while (work2do > 0 && g->gcstate != GCSpause);
if (g->gcstate == GCSpause)
setpause(g); /* pause until next cycle */
else {
debt = (debt / stepmul) * 100; /* apply step multiplier */
luaE_setdebt(g, debt);
luaE_setdebt(g, -stepsize);
}
}