in case 1,
my process stops lua-gc, and do step-gc in lua by calling collectgarbage.
it run normally in lua5.3.5 by default gc param. (gc cost is 1%)
but when it run in lua5.4.3 by default gc param. lua gc cost is very high (22%)
i found debt is divided by STEPMULADJ in lua5.3.6 :
```
static l_mem getdebt (global_State *g) {
l_mem debt = g->GCdebt;
int stepmul = g->gcstepmul;
if (debt <= 0) return 0; /* minimal debt */
else {
debt = (debt / STEPMULADJ) + 1;
debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM;
return debt;
}
}
```
but there is no such code in lua5.4.3.
the process run normally in lua5.4.3 when debt divided by LUAI_GCMUL
2. in case 2.
the size of gc step does't meet the expectation. i.e. when i call collectgarbage("step", step_size),
the actual size of step is much larger than step_size
i found that it reset gc debt when gc is stopped in lua5.3.5
```
void luaC_step (lua_State *L) {
global_State *g = G(L);
l_mem debt = getdebt(g); /* GC deficit (be paid now) */
if (!g->gcrunning) { /* not running? */
luaE_setdebt(g, -GCSTEPSIZE * 10); /* avoid being called too often */
return;
}
do { /* repeat until pause or enough "credit" (negative debt) */
lu_mem work = singlestep(L); /* perform one single step */
debt -= work;
} while (debt > -GCSTEPSIZE && g->gcstate != GCSpause);
if (g->gcstate == GCSpause)
setpause(g); /* pause until next cycle */
else {
debt = (debt / g->gcstepmul) * STEPMULADJ; /* convert 'work units' to Kb */
luaE_setdebt(g, debt);
runafewfinalizers(L);
}
}
```
but there is no this code in lua5.4.3
when I add the reset code in lua5.4.3
the process
collectgarbage by step_size as expectation.
