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revamp of the GC pace control; more like 5.1: any X Kbytes allocated

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makes the GC handle f(X) Kbytes of objects
This commit is contained in:
Roberto Ierusalimschy
2012-05-20 17:36:44 -03:00
parent 8d0e1ed52f
commit 2a66b34f72
2 changed files with 120 additions and 97 deletions
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213
lgc.c
View File

@@ -1,5 +1,5 @@
/* /*
** $Id: lgc.c,v 2.121 2012/05/11 19:22:33 roberto Exp roberto $ ** $Id: lgc.c,v 2.122 2012/05/14 17:52:56 roberto Exp roberto $
** Garbage Collector ** Garbage Collector
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@@ -25,33 +25,36 @@
/* how much to allocate before next GC step */ /* how much to allocate before next GC step */
#define GCSTEPSIZE 1024 #define GCSTEPSIZE (cast_int(256 * sizeof(void*)))
/* cost of sweeping one element (half the size of a small object) */
#define GCSWEEPCOST ((sizeof(TString) + 2) / 2)
/* maximum number of elements to sweep in each single step */ /* maximum number of elements to sweep in each single step */
#define GCSWEEPMAX 40 #define GCSWEEPMAX (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4))
/* cost of sweeping one element */
#define GCSWEEPCOST 1
/* maximum number of finalizers to call in each GC step */ /* maximum number of finalizers to call in each GC step */
#define GCFINALIZENUM 4 #define GCFINALIZENUM 4
/* cost of marking the root set */ /* (arbitrary) cost of atomic step */
#define GCROOTCOST 10 #define GCATOMICCOST GCSTEPSIZE
/* cost of atomic step */
#define GCATOMICCOST 1000
/* basic cost to traverse one object (to be added to the links the
object may have) */
#define TRAVCOST 5
/*
** macro to apply the "speed" of the garbage collector: the constant
** 80 makes the standard 'stepmul' of 200 results in the GC handling
** 80/200 = 1/2.5 = 0.4Kbytes for every 1Kb allocated.
** (The computation tries to avoid overflows or underflows.)
*/
#define workrate(x,mul) \
((x) < MAX_INT/80 ? ((x) * 80) / mul : ((x) / mul) * 80)
/* /*
** standard negative debt for GC; a reasonable "time" to wait before ** standard negative debt for GC; a reasonable "time" to wait before
** starting a new cycle ** starting a new cycle
*/ */
#define stddebt(g) (-cast(l_mem, gettotalbytes(g)/100) * g->gcpause) #define stddebtest(g,e) (-cast(l_mem, (e)/100) * g->gcpause)
#define stddebt(g) stddebtest(g, gettotalbytes(g))
/* /*
@@ -244,53 +247,57 @@ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz, GCObject **list,
** upvalues are already linked in 'headuv' list.) ** upvalues are already linked in 'headuv' list.)
*/ */
static void reallymarkobject (global_State *g, GCObject *o) { static void reallymarkobject (global_State *g, GCObject *o) {
lu_mem size;
white2gray(o); white2gray(o);
switch (gch(o)->tt) { switch (gch(o)->tt) {
case LUA_TSHRSTR: case LUA_TSHRSTR:
case LUA_TLNGSTR: { case LUA_TLNGSTR: {
gray2black(o); size = sizestring(gco2ts(o));
return; /* nothing else to mark */ break; /* nothing else to mark; make it black */
} }
case LUA_TUSERDATA: { case LUA_TUSERDATA: {
Table *mt = gco2u(o)->metatable; Table *mt = gco2u(o)->metatable;
markobject(g, mt); markobject(g, mt);
markobject(g, gco2u(o)->env); markobject(g, gco2u(o)->env);
gray2black(o); /* all pointers marked */ size = sizeudata(gco2u(o));
return; break;
} }
case LUA_TUPVAL: { case LUA_TUPVAL: {
UpVal *uv = gco2uv(o); UpVal *uv = gco2uv(o);
markvalue(g, uv->v); markvalue(g, uv->v);
if (uv->v == &uv->u.value) /* closed? (open upvalues remain gray) */ if (uv->v != &uv->u.value) /* open? */
gray2black(o); /* make it black */ return; /* open upvalues remain gray */
return; size = sizeof(UpVal);
break;
} }
case LUA_TLCL: { case LUA_TLCL: {
gco2lcl(o)->gclist = g->gray; gco2lcl(o)->gclist = g->gray;
g->gray = o; g->gray = o;
break; return;
} }
case LUA_TCCL: { case LUA_TCCL: {
gco2ccl(o)->gclist = g->gray; gco2ccl(o)->gclist = g->gray;
g->gray = o; g->gray = o;
break; return;
} }
case LUA_TTABLE: { case LUA_TTABLE: {
linktable(gco2t(o), &g->gray); linktable(gco2t(o), &g->gray);
break; return;
} }
case LUA_TTHREAD: { case LUA_TTHREAD: {
gco2th(o)->gclist = g->gray; gco2th(o)->gclist = g->gray;
g->gray = o; g->gray = o;
break; return;
} }
case LUA_TPROTO: { case LUA_TPROTO: {
gco2p(o)->gclist = g->gray; gco2p(o)->gclist = g->gray;
g->gray = o; g->gray = o;
break; return;
} }
default: lua_assert(0); default: lua_assert(0); return;
} }
gray2black(o);
g->GCmemtrav += size;
} }
@@ -430,30 +437,26 @@ static void traversestrongtable (global_State *g, Table *h) {
} }
static int traversetable (global_State *g, Table *h) { static lu_mem traversetable (global_State *g, Table *h) {
char *weakkey, *weakvalue;
const TValue *mode = gfasttm(g, h->metatable, TM_MODE); const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
markobject(g, h->metatable); markobject(g, h->metatable);
if (mode && ttisstring(mode)) { /* is there a weak mode? */ if (mode && ttisstring(mode) && /* is there a weak mode? */
int weakkey = (strchr(svalue(mode), 'k') != NULL); ((weakkey = strchr(svalue(mode), 'k')),
int weakvalue = (strchr(svalue(mode), 'v') != NULL); (weakvalue = strchr(svalue(mode), 'v')),
if (weakkey || weakvalue) { /* is really weak? */ (weakkey || weakvalue))) { /* is really weak? */
black2gray(obj2gco(h)); /* keep table gray */ black2gray(obj2gco(h)); /* keep table gray */
if (!weakkey) { /* strong keys? */ if (!weakkey) /* strong keys? */
traverseweakvalue(g, h); traverseweakvalue(g, h);
return TRAVCOST + sizenode(h); else if (!weakvalue) /* strong values? */
} traverseephemeron(g, h);
else if (!weakvalue) { /* strong values? */ else /* all weak */
traverseephemeron(g, h); linktable(h, &g->allweak); /* nothing to traverse now */
return TRAVCOST + h->sizearray + sizenode(h);
}
else {
linktable(h, &g->allweak); /* nothing to traverse now */
return TRAVCOST;
}
} /* else go through */
} }
traversestrongtable(g, h); else /* not weak */
return TRAVCOST + h->sizearray + (2 * sizenode(h)); traversestrongtable(g, h);
return sizeof(Table) + sizeof(TValue) * h->sizearray +
sizeof(Node) * sizenode(h);
} }
@@ -470,81 +473,92 @@ static int traverseproto (global_State *g, Proto *f) {
markobject(g, f->p[i]); markobject(g, f->p[i]);
for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */ for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */
markobject(g, f->locvars[i].varname); markobject(g, f->locvars[i].varname);
return TRAVCOST + f->sizek + f->sizeupvalues + f->sizep + f->sizelocvars; return sizeof(Proto) + sizeof(Instruction) * f->sizecode +
sizeof(Proto *) * f->sizep +
sizeof(TValue) * f->sizek +
sizeof(int) * f->sizelineinfo +
sizeof(LocVar) * f->sizelocvars +
sizeof(Upvaldesc) * f->sizeupvalues;
} }
static int traverseCclosure (global_State *g, CClosure *cl) { static lu_mem traverseCclosure (global_State *g, CClosure *cl) {
int i; int i;
for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */ for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
markvalue(g, &cl->upvalue[i]); markvalue(g, &cl->upvalue[i]);
return TRAVCOST + cl->nupvalues; return sizeCclosure(cl->nupvalues);
} }
static int traverseLclosure (global_State *g, LClosure *cl) { static lu_mem traverseLclosure (global_State *g, LClosure *cl) {
int i; int i;
markobject(g, cl->p); /* mark its prototype */ markobject(g, cl->p); /* mark its prototype */
for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */ for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
markobject(g, cl->upvals[i]); markobject(g, cl->upvals[i]);
return TRAVCOST + cl->nupvalues; return sizeLclosure(cl->nupvalues);
} }
static int traversestack (global_State *g, lua_State *L) { static lu_mem traversestack (global_State *g, lua_State *th) {
StkId o = L->stack; StkId o = th->stack;
if (o == NULL) if (o == NULL)
return 1; /* stack not completely built yet */ return 1; /* stack not completely built yet */
for (; o < L->top; o++) for (; o < th->top; o++)
markvalue(g, o); markvalue(g, o);
if (g->gcstate == GCSatomic) { /* final traversal? */ if (g->gcstate == GCSatomic) { /* final traversal? */
StkId lim = L->stack + L->stacksize; /* real end of stack */ StkId lim = th->stack + th->stacksize; /* real end of stack */
for (; o < lim; o++) /* clear not-marked stack slice */ for (; o < lim; o++) /* clear not-marked stack slice */
setnilvalue(o); setnilvalue(o);
} }
return TRAVCOST + cast_int(o - L->stack); return sizeof(lua_State) + sizeof(TValue) * th->stacksize;
} }
/* /*
** traverse one gray object, turning it to black (except for threads, ** traverse one gray object, turning it to black (except for threads,
** which are always gray). ** which are always gray).
** Returns number of values traversed.
*/ */
static int propagatemark (global_State *g) { static void propagatemark (global_State *g) {
lu_mem size;
GCObject *o = g->gray; GCObject *o = g->gray;
lua_assert(isgray(o)); lua_assert(isgray(o));
gray2black(o); gray2black(o);
switch (gch(o)->tt) { switch (gch(o)->tt) {
case LUA_TTABLE: { case LUA_TTABLE: {
Table *h = gco2t(o); Table *h = gco2t(o);
g->gray = h->gclist; g->gray = h->gclist; /* remove from 'gray' list */
return traversetable(g, h); size = traversetable(g, h);
break;
} }
case LUA_TLCL: { case LUA_TLCL: {
LClosure *cl = gco2lcl(o); LClosure *cl = gco2lcl(o);
g->gray = cl->gclist; g->gray = cl->gclist; /* remove from 'gray' list */
return traverseLclosure(g, cl); size = traverseLclosure(g, cl);
break;
} }
case LUA_TCCL: { case LUA_TCCL: {
CClosure *cl = gco2ccl(o); CClosure *cl = gco2ccl(o);
g->gray = cl->gclist; g->gray = cl->gclist; /* remove from 'gray' list */
return traverseCclosure(g, cl); size = traverseCclosure(g, cl);
break;
} }
case LUA_TTHREAD: { case LUA_TTHREAD: {
lua_State *th = gco2th(o); lua_State *th = gco2th(o);
g->gray = th->gclist; g->gray = th->gclist; /* remove from 'gray' list */
th->gclist = g->grayagain; th->gclist = g->grayagain;
g->grayagain = o; g->grayagain = o; /* insert into 'grayagain' list */
black2gray(o); black2gray(o);
return traversestack(g, th); size = traversestack(g, th);
break;
} }
case LUA_TPROTO: { case LUA_TPROTO: {
Proto *p = gco2p(o); Proto *p = gco2p(o);
g->gray = p->gclist; g->gray = p->gclist; /* remove from 'gray' list */
return traverseproto(g, p); size = traverseproto(g, p);
break;
} }
default: lua_assert(0); return 0; default: lua_assert(0); return;
} }
g->GCmemtrav += size;
} }
@@ -706,7 +720,6 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
int ow = otherwhite(g); int ow = otherwhite(g);
int toclear, toset; /* bits to clear and to set in all live objects */ int toclear, toset; /* bits to clear and to set in all live objects */
int tostop; /* stop sweep when this is true */ int tostop; /* stop sweep when this is true */
l_mem debt = g->GCdebt; /* current debt */
if (isgenerational(g)) { /* generational mode? */ if (isgenerational(g)) { /* generational mode? */
toclear = ~0; /* clear nothing */ toclear = ~0; /* clear nothing */
toset = bitmask(OLDBIT); /* set the old bit of all surviving objects */ toset = bitmask(OLDBIT); /* set the old bit of all surviving objects */
@@ -737,7 +750,6 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
p = &gch(curr)->next; /* go to next element */ p = &gch(curr)->next; /* go to next element */
} }
} }
luaE_setdebt(g, debt); /* sweeping should not change debt */
return p; return p;
} }
@@ -960,37 +972,42 @@ static void atomic (lua_State *L) {
} }
static l_mem singlestep (lua_State *L) { static lu_mem singlestep (lua_State *L) {
global_State *g = G(L); global_State *g = G(L);
switch (g->gcstate) { switch (g->gcstate) {
case GCSpause: { case GCSpause: {
g->GCmemtrav = 0; /* start to count memory traversed */
if (!isgenerational(g)) if (!isgenerational(g))
markroot(g); /* start a new collection */ markroot(g); /* start a new collection */
/* in any case, root must be marked */ /* in any case, root must be marked at this point */
lua_assert(!iswhite(obj2gco(g->mainthread)) lua_assert(!iswhite(obj2gco(g->mainthread))
&& !iswhite(gcvalue(&g->l_registry))); && !iswhite(gcvalue(&g->l_registry)));
g->gcstate = GCSpropagate; g->gcstate = GCSpropagate;
return GCROOTCOST; return g->GCmemtrav;
} }
case GCSpropagate: { case GCSpropagate: {
if (g->gray) if (g->gray) {
return propagatemark(g); lu_mem oldtrav = g->GCmemtrav;
propagatemark(g);
return g->GCmemtrav - oldtrav; /* memory traversed in this step */
}
else { /* no more `gray' objects */ else { /* no more `gray' objects */
g->gcstate = GCSatomic; /* finish mark phase */ g->gcstate = GCSatomic; /* finish mark phase */
g->estimate = g->GCmemtrav; /* save what was counted */
atomic(L); atomic(L);
return GCATOMICCOST; return GCATOMICCOST;
} }
} }
case GCSsweepstring: { case GCSsweepstring: {
if (g->sweepstrgc < g->strt.size) { int i;
sweepwholelist(L, &g->strt.hash[g->sweepstrgc++]); for (i = 0; i < GCSWEEPMAX && g->sweepstrgc + i < g->strt.size; i++)
return GCSWEEPCOST; sweepwholelist(L, &g->strt.hash[g->sweepstrgc + i]);
} g->sweepstrgc += i;
else { /* no more strings to sweep */ if (g->sweepstrgc >= g->strt.size) { /* no more strings to sweep? */
g->sweepgc = &g->finobj; /* prepare to sweep finalizable objects */ g->sweepgc = &g->finobj; /* prepare to sweep finalizable objects */
g->gcstate = GCSsweepudata; g->gcstate = GCSsweepudata;
return 0;
} }
return i * GCSWEEPCOST;
} }
case GCSsweepudata: { case GCSsweepudata: {
if (*g->sweepgc) { if (*g->sweepgc) {
@@ -1000,7 +1017,7 @@ static l_mem singlestep (lua_State *L) {
else { else {
g->sweepgc = &g->allgc; /* go to next phase */ g->sweepgc = &g->allgc; /* go to next phase */
g->gcstate = GCSsweep; g->gcstate = GCSsweep;
return GCSWEEPCOST; return 0;
} }
} }
case GCSsweep: { case GCSsweep: {
@@ -1051,14 +1068,17 @@ static void generationalcollection (lua_State *L) {
static void step (lua_State *L) { static void step (lua_State *L) {
global_State *g = G(L); global_State *g = G(L);
l_mem lim = g->gcstepmul; /* how much to work */ l_mem debt = g->GCdebt;
int stepmul = g->gcstepmul;
if (stepmul <= 0) stepmul = 1;
do { /* always perform at least one single step */ do { /* always perform at least one single step */
lim -= singlestep(L); lu_mem work = singlestep(L); /* do some work */
} while (lim > 0 && g->gcstate != GCSpause); work = workrate(work, stepmul); /* apply work rate */
if (g->gcstate != GCSpause) debt -= work;
luaE_setdebt(g, g->GCdebt - GCSTEPSIZE); } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause);
else if (g->gcstate == GCSpause)
luaE_setdebt(g, stddebt(g)); debt = stddebtest(g, g->estimate); /* pause until next cycle */
luaE_setdebt(g, debt);
} }
@@ -1070,8 +1090,9 @@ void luaC_step (lua_State *L) {
int i; int i;
if (isgenerational(g)) generationalcollection(L); if (isgenerational(g)) generationalcollection(L);
else step(L); else step(L);
for (i = 0; i < GCFINALIZENUM && g->tobefnz; i++) /* run a few finalizers (or all of them at the end of a collect cycle) */
GCTM(L, 1); /* Call a few pending finalizers */ for (i = 0; g->tobefnz && (i < GCFINALIZENUM || g->gcstate == GCSpause); i++)
GCTM(L, 1); /* call one finalizer */
} }

4
lstate.h
View File

@@ -1,5 +1,5 @@
/* /*
** $Id: lstate.h,v 2.76 2012/01/25 21:05:40 roberto Exp roberto $ ** $Id: lstate.h,v 2.77 2012/02/01 21:57:15 roberto Exp roberto $
** Global State ** Global State
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@@ -113,7 +113,9 @@ typedef struct global_State {
void *ud; /* auxiliary data to `frealloc' */ void *ud; /* auxiliary data to `frealloc' */
lu_mem totalbytes; /* number of bytes currently allocated - GCdebt */ lu_mem totalbytes; /* number of bytes currently allocated - GCdebt */
l_mem GCdebt; /* bytes allocated not yet compensated by the collector */ l_mem GCdebt; /* bytes allocated not yet compensated by the collector */
lu_mem GCmemtrav; /* memory traversed by the GC */
lu_mem lastmajormem; /* memory in use after last major collection */ lu_mem lastmajormem; /* memory in use after last major collection */
lu_mem estimate;
stringtable strt; /* hash table for strings */ stringtable strt; /* hash table for strings */
TValue l_registry; TValue l_registry;
unsigned int seed; /* randomized seed for hashes */ unsigned int seed; /* randomized seed for hashes */