New option "setparms" for 'collectgarbage'

The generational mode also uses the parameters for the incremental
mode in its major collections, so it should be easy to change those
parameters without having to change the GC mode.

lapi.c

@@ -1186,27 +1186,37 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
       break;
     }
     case LUA_GCGEN: {
+#if defined(LUA_COMPAT_GCPARAMS)
       int minormul = va_arg(argp, int);
       int minormajor = va_arg(argp, int);
-      int majorminor = va_arg(argp, int);
+      if (minormul > 0) setgcparam(g, MINORMUL, minormul);
+      if (minormajor > 0) setgcparam(g, MINORMAJOR, minormajor);
+#endif
       res = (g->gckind == KGC_INC) ? LUA_GCINC : LUA_GCGEN;
-      setgcparam(g, gcpgenminormul, minormul);
-      setgcparam(g, gcpminormajor, minormajor);
-      setgcparam(g, gcpmajorminor, majorminor);
       luaC_changemode(L, KGC_GENMINOR);
       break;
     }
     case LUA_GCINC: {
+#if defined(LUA_COMPAT_GCPARAMS)
       int pause = va_arg(argp, int);
       int stepmul = va_arg(argp, int);
       int stepsize = va_arg(argp, int);
+      if (pause > 0) setgcparam(g, PAUSE, pause);
+      if (stepmul > 0) setgcparam(g, STEPMUL, stepmul);
+      if (stepsize > 0) setgcparam(g, STEPSIZE, 1u << stepsize);
+#endif
       res = (g->gckind == KGC_INC) ? LUA_GCINC : LUA_GCGEN;
-      setgcparam(g, gcppause, pause);
-      setgcparam(g, gcpstepmul, stepmul);
-      setgcparam(g, gcpstepsize, stepsize);
       luaC_changemode(L, KGC_INC);
       break;
     }
+    case LUA_GCSETPARAM: {
+      int param = va_arg(argp, int);
+      int value = va_arg(argp, int);
+      api_check(L, 0 <= param && param < LUA_GCPN, "invalid parameter");
+      res = luaO_applyparam(g->gcparams[param], 100);
+      g->gcparams[param] = luaO_codeparam(value);
+      break;
+    }
     default: res = -1;  /* invalid option */
   }
   va_end(argp);

lbaselib.c

@@ -198,9 +198,11 @@ static int pushmode (lua_State *L, int oldmode) {
 
 static int luaB_collectgarbage (lua_State *L) {
   static const char *const opts[] = {"stop", "restart", "collect",
-    "count", "step", "isrunning", "generational", "incremental", NULL};
-  static const int optsnum[] = {LUA_GCSTOP, LUA_GCRESTART, LUA_GCCOLLECT,
-    LUA_GCCOUNT, LUA_GCSTEP, LUA_GCISRUNNING, LUA_GCGEN, LUA_GCINC};
+    "count", "step", "isrunning", "generational", "incremental",
+    "setparam", NULL};
+  static const char optsnum[] = {LUA_GCSTOP, LUA_GCRESTART, LUA_GCCOLLECT,
+    LUA_GCCOUNT, LUA_GCSTEP, LUA_GCISRUNNING, LUA_GCGEN, LUA_GCINC,
+    LUA_GCSETPARAM};
   int o = optsnum[luaL_checkoption(L, 1, "collect", opts)];
   switch (o) {
     case LUA_GCCOUNT: {
@@ -224,17 +226,39 @@ static int luaB_collectgarbage (lua_State *L) {
       return 1;
     }
     case LUA_GCGEN: {
+#if defined(LUA_COMPAT_GCPARAMS)
       int minormul = (int)luaL_optinteger(L, 2, -1);
       int majorminor = (int)luaL_optinteger(L, 3, -1);
-      int minormajor = (int)luaL_optinteger(L, 4, -1);
-      return pushmode(L, lua_gc(L, o, minormul, majorminor, minormajor));
+#else
+      int minormul = 0;
+      int majorminor = 0;
+#endif
+      return pushmode(L, lua_gc(L, o, minormul, majorminor));
     }
     case LUA_GCINC: {
+#if defined(LUA_COMPAT_GCPARAMS)
       int pause = (int)luaL_optinteger(L, 2, -1);
       int stepmul = (int)luaL_optinteger(L, 3, -1);
       int stepsize = (int)luaL_optinteger(L, 4, -1);
+#else
+      int pause = 0;
+      int stepmul = 0;
+      int stepsize = 0;
+#endif
       return pushmode(L, lua_gc(L, o, pause, stepmul, stepsize));
     }
+    case LUA_GCSETPARAM: {
+      static const char *const params[] = {
+        "minormul", "majorminor", "minormajor",
+        "pause", "stepmul", "stepsize", NULL};
+      static const char pnum[] = {
+        LUA_GCPMINORMUL, LUA_GCPMAJORMINOR, LUA_GCPMINORMAJOR,
+        LUA_GCPPAUSE, LUA_GCPSTEPMUL, LUA_GCPSTEPSIZE};
+      int p = pnum[luaL_checkoption(L, 2, NULL, params)];
+      lua_Integer value = luaL_checkinteger(L, 3);
+      lua_pushinteger(L, lua_gc(L, o, p, value));
+      return 1;
+    }
     default: {
       int res = lua_gc(L, o);
       checkvalres(res);

lgc.c

@@ -1049,7 +1049,7 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
 ** approximately (marked * pause / 100).
 */
 static void setpause (global_State *g) {
-  l_obj threshold = luaO_applyparam(g->gcppause, g->marked);
+  l_obj threshold = applygcparam(g, PAUSE, g->marked);
   l_obj debt = threshold - gettotalobjs(g);
   if (debt < 0) debt = 0;
   luaE_setdebt(g, debt);
@@ -1239,7 +1239,7 @@ static void minor2inc (lua_State *L, global_State *g, int kind) {
   g->finobjrold = g->finobjold1 = g->finobjsur = NULL;
   entersweep(L);  /* continue as an incremental cycle */
   /* set a debt equal to the step size */
-  luaE_setdebt(g, luaO_applyparam(g->gcpstepsize, 100));
+  luaE_setdebt(g, applygcparam(g, STEPSIZE, 100));
 }
 
 
@@ -1255,8 +1255,8 @@ static void minor2inc (lua_State *L, global_State *g, int kind) {
 ** major collection. (That percentage is computed in 'limit'.)
 */
 static int checkminormajor (lua_State *L, global_State *g, l_obj addedold1) {
-  l_obj step = luaO_applyparam(g->gcpgenminormul, g->GCmajorminor);
-  l_obj limit = luaO_applyparam(g->gcpminormajor, g->GCmajorminor);
+  l_obj step = applygcparam(g, MINORMUL, g->GCmajorminor);
+  l_obj limit = applygcparam(g, MINORMAJOR, g->GCmajorminor);
 //printf("-> major? %ld %ld %ld %ld (%ld)\n", g->marked, limit, step, addedold1, gettotalobjs(g));
   if (addedold1 >= (step >> 1) || g->marked >= limit) {
     minor2inc(L, g, KGC_GENMAJOR);  /* go to major mode */
@@ -1347,7 +1347,7 @@ static void atomic2gen (lua_State *L, global_State *g) {
 ** total number of objects grows 'genminormul'%.
 */
 static void setminordebt (global_State *g) {
-  luaE_setdebt(g, luaO_applyparam(g->gcpgenminormul, g->GCmajorminor));
+  luaE_setdebt(g, applygcparam(g, MINORMUL, g->GCmajorminor));
 }
 
 
@@ -1404,7 +1404,7 @@ static int checkmajorminor (lua_State *L, global_State *g) {
   if (g->gckind == KGC_GENMAJOR) {
     l_obj numobjs = gettotalobjs(g);
     l_obj addedobjs = numobjs - g->GCmajorminor;
-    l_obj limit = luaO_applyparam(g->gcpmajorminor, addedobjs);
+    l_obj limit = applygcparam(g, MAJORMINOR, addedobjs);
     l_obj tobecollected = numobjs - g->marked;
 //printf("-> minor? %ld %ld %ld\n", tobecollected, limit, numobjs);
     if (tobecollected > limit) {
@@ -1634,8 +1634,8 @@ void luaC_runtilstate (lua_State *L, int state, int fast) {
 ** controls when next step will be performed.
 */
 static void incstep (lua_State *L, global_State *g) {
-  l_obj stepsize = luaO_applyparam(g->gcpstepsize, 100);
-  l_obj work2do = luaO_applyparam(g->gcpstepmul, stepsize);
+  l_obj stepsize = applygcparam(g, STEPSIZE, 100);
+  l_obj work2do = applygcparam(g, STEPMUL, stepsize);
   int fast = 0;
   if (work2do == 0) {  /* special case: do a full collection */
     work2do = MAX_LOBJ;  /* do unlimited work */

lgc.h

@@ -193,7 +193,8 @@
 #define LUAI_GCSTEPSIZE	250
 
 
-#define setgcparam(g,p,v)	if ((v) >= 0) {g->p = luaO_codeparam(v);}
+#define setgcparam(g,p,v)  (g->gcparams[LUA_GCP##p] = luaO_codeparam(v))
+#define applygcparam(g,p,x)  luaO_applyparam(g->gcparams[LUA_GCP##p], x)
 
 /*
 ** Control when GC is running:

lstate.c

@@ -365,12 +365,12 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud, unsigned int seed) {
   g->marked = 0;
   g->GCdebt = 0;
   setivalue(&g->nilvalue, 0);  /* to signal that state is not yet built */
-  setgcparam(g, gcppause, LUAI_GCPAUSE);
-  setgcparam(g, gcpstepmul, LUAI_GCMUL);
-  setgcparam(g, gcpstepsize, LUAI_GCSTEPSIZE);
-  setgcparam(g, gcpgenminormul, LUAI_GENMINORMUL);
-  setgcparam(g, gcpminormajor, LUAI_MINORMAJOR);
-  setgcparam(g, gcpmajorminor, LUAI_MAJORMINOR);
+  setgcparam(g, PAUSE, LUAI_GCPAUSE);
+  setgcparam(g, STEPMUL, LUAI_GCMUL);
+  setgcparam(g, STEPSIZE, LUAI_GCSTEPSIZE);
+  setgcparam(g, MINORMUL, LUAI_GENMINORMUL);
+  setgcparam(g, MINORMAJOR, LUAI_MINORMAJOR);
+  setgcparam(g, MAJORMINOR, LUAI_MAJORMINOR);
   for (i=0; i < LUA_NUMTAGS; i++) g->mt[i] = NULL;
   if (luaD_rawrunprotected(L, f_luaopen, NULL) != LUA_OK) {
     /* memory allocation error: free partial state */

lstate.h

@@ -264,12 +264,7 @@ typedef struct global_State {
   TValue l_registry;
   TValue nilvalue;  /* a nil value */
   unsigned int seed;  /* randomized seed for hashes */
-  lu_byte gcpgenminormul;  /* control minor generational collections */
-  lu_byte gcpmajorminor;  /* control shift major->minor */
-  lu_byte gcpminormajor;  /* control shift minor->major */
-  lu_byte gcppause;  /* size of pause between successive GCs */
-  lu_byte gcpstepmul;  /* GC "speed" */
-  lu_byte gcpstepsize;  /* GC granularity */
+  lu_byte gcparams[LUA_GCPN];
   lu_byte currentwhite;
   lu_byte gcstate;  /* state of garbage collector */
   lu_byte gckind;  /* kind of GC running */

ltests.c

@@ -1037,12 +1037,12 @@ static int query_GCparams (lua_State *L) {
   global_State *g = G(L);
   lua_pushinteger(L, gettotalobjs(g));
   lua_pushinteger(L, g->GCdebt);
-  lua_pushinteger(L, luaO_applyparam(g->gcpgenminormul, 100));
-  lua_pushinteger(L, luaO_applyparam(g->gcpmajorminor, 100));
-  lua_pushinteger(L, luaO_applyparam(g->gcpminormajor, 100));
-  lua_pushinteger(L, luaO_applyparam(g->gcppause, 100));
-  lua_pushinteger(L, luaO_applyparam(g->gcpstepmul, 100));
-  lua_pushinteger(L, luaO_applyparam(g->gcpstepsize, 100));
+  lua_pushinteger(L, applygcparam(g, MINORMUL, 100));
+  lua_pushinteger(L, applygcparam(g, MAJORMINOR, 100));
+  lua_pushinteger(L, applygcparam(g, MINORMAJOR, 100));
+  lua_pushinteger(L, applygcparam(g, PAUSE, 100));
+  lua_pushinteger(L, applygcparam(g, STEPMUL, 100));
+  lua_pushinteger(L, applygcparam(g, STEPSIZE, 100));
   return 8;
 }
 

ltests.h

@@ -15,6 +15,8 @@
 #define LUA_COMPAT_MATHLIB
 #define LUA_COMPAT_LT_LE
 
+#define LUA_COMPAT_GCPARAMS
+
 
 #define LUA_DEBUG
 

lua.c

@@ -646,7 +646,7 @@ static int pmain (lua_State *L) {
   luai_openlibs(L);  /* open standard libraries */
   createargtable(L, argv, argc, script);  /* create table 'arg' */
   lua_gc(L, LUA_GCRESTART);  /* start GC... */
-  lua_gc(L, LUA_GCGEN, -1, -1, -1);  /* ...in generational mode */
+  lua_gc(L, LUA_GCGEN, 0, 0);  /* ...in generational mode */
   if (!(args & has_E)) {  /* no option '-E'? */
     if (handle_luainit(L) != LUA_OK)  /* run LUA_INIT */
       return 0;  /* error running LUA_INIT */

lua.h

@@ -325,7 +325,7 @@ LUA_API void (lua_warning)  (lua_State *L, const char *msg, int tocont);
 
 
 /*
-** garbage-collection function and options
+** garbage-collection options
 */
 
 #define LUA_GCSTOP		0
@@ -337,6 +337,25 @@ LUA_API void (lua_warning)  (lua_State *L, const char *msg, int tocont);
 #define LUA_GCISRUNNING		6
 #define LUA_GCGEN		7
 #define LUA_GCINC		8
+#define LUA_GCSETPARAM		9
+
+
+/*
+** garbage-collection parameters
+*/
+/* parameters for generational mode */
+#define LUA_GCPMINORMUL		0  /* control minor collections */
+#define LUA_GCPMAJORMINOR	1  /* control shift major->minor */
+#define LUA_GCPMINORMAJOR	2  /* control shift minor->major */
+
+/* parameters for incremental mode */
+#define LUA_GCPPAUSE		3  /* size of pause between successive GCs */
+#define LUA_GCPSTEPMUL		4  /* GC "speed" */
+#define LUA_GCPSTEPSIZE		5  /* GC granularity */
+
+/* number of parameters */
+#define LUA_GCPN		6
+
 
 LUA_API int (lua_gc) (lua_State *L, int what, ...);
 

manual/manual.of

@@ -681,12 +681,10 @@ effectively producing a non-incremental, stop-the-world collector.
 The garbage-collector step size controls the
 size of each incremental step,
 specifically how many objects the interpreter creates
-before performing a step.
-This parameter is logarithmic:
-A value of @M{n} means the interpreter will create @M{2@sp{n}}
-objects between steps.
-The default value is 8,
-which means steps of approximately @N{256 objects}.
+before performing a step:
+A value of @M{n} means the interpreter will create
+approximately @M{n} objects between steps.
+The default value is 250.
 
 }
 
@@ -728,11 +726,13 @@ The default value is 100.
 The major-minor multiplier controls the shift back to minor collections.
 For a multiplier @M{x},
 the collector will shift back to minor collections
-after a major collection collects at least @M{x%} of the allocated objects.
+after a major collection collects at least @M{x%}
+of the objects allocated during the last cycle.
+
 In particular, for a multiplier of 0,
 the collector will immediately shift back to minor collections
 after doing one cycle of major collections.
-The default value is 20.
+The default value is 80.
 
 }
 
@@ -3336,19 +3336,32 @@ Returns a boolean that tells whether the collector is running
 (i.e., not stopped).
 }
 
-@item{@defid{LUA_GCINC} (int pause, int stepmul, int stepsize)|
-Changes the collector to incremental mode
-with the given parameters @see{incmode}.
+@item{@defid{LUA_GCINC}|
+Changes the collector to incremental mode.
 Returns the previous mode (@id{LUA_GCGEN} or @id{LUA_GCINC}).
 }
 
-@item{@defid{LUA_GCGEN} (int minormul, int minormajor, int majorminor)|
-Changes the collector to generational mode
-with the given parameters @see{genmode}.
+@item{@defid{LUA_GCGEN}|
+Changes the collector to generational mode.
 Returns the previous mode (@id{LUA_GCGEN} or @id{LUA_GCINC}).
 }
 
+@item{@defid{LUA_GCSETPARAM} (int param, int value)|
+Changes the values of a parameter of the collector and returns
+the previous value of that parameter.
+The argument @id{param} must have one of the following values:
+@description{
+@item{@defid{LUA_GCPMINORMUL}| The minor multiplier. }
+@item{@defid{LUA_GCPMAJORMINOR}| The major-minor multiplier. }
+@item{@defid{LUA_GCPMINORMAJOR}| The minor-major multiplier. }
+@item{@defid{LUA_GCPPAUSE}| The garbage-collector pause. }
+@item{@defid{LUA_GCPSTEPMUL}| The step multiplier. }
+@item{@defid{LUA_GCPSTEPSIZE}| The step size. }
+}
+}
+
 }
+
 For more details about these options,
 see @Lid{collectgarbage}.
 
@@ -6347,20 +6360,35 @@ Returns a boolean that tells whether the collector is running
 }
 
 @item{@St{incremental}|
-Change the collector mode to incremental.
-This option can be followed by three numbers:
-the garbage-collector pause,
-the step multiplier,
-and the step size @see{incmode}.
-A -1 or absent value means to not change that value.
+Changes the collector mode to incremental and returns the previous mode.
 }
 
 @item{@St{generational}|
-Change the collector mode to generational.
-This option can be followed by three numbers:
-the garbage-collector minor multiplier,
-the minor-major multiplier, and the major-minor multiplier @see{genmode}.
-A -1 or absent value means to not change that value.
+Changes the collector mode to generational and returns the previous mode.
+}
+
+@item{@St{setparam}|
+Changes the values of a parameter of the collector and returns
+the previous value of that parameter.
+This option must be followed by two extra arguments:
+The name of the parameter being changed (a string)
+and the new value for that parameter (an integer).
+The argument @id{param} must have one of the following values:
+@description{
+@item{@St{minormul}| The minor multiplier. }
+@item{@St{majorminor}| The major-minor multiplier. }
+@item{@St{minormajor}| The minor-major multiplier. }
+@item{@St{pause}| The garbage-collector pause. }
+@item{@St{stepmul}| The step multiplier. }
+@item{@St{stepsize}| The step size. }
+}
+To be able to divide by 100
+(as most parameters are given as percentages)
+without using floating-point arithmetic,
+Lua stores these parameters encoded.
+This encoding approximates the real value;
+so, the value returned as the previous value may not be
+equal to the last value set.
 }
 
 }
@@ -9249,9 +9277,10 @@ declare a local variable with the same name in the loop body.
 @itemize{
 
 @item{
-There were several changes in the parameters
-for the options @St{incremental} and @St{generational}
-of the function @Lid{collectgarbage}.
+Parameters for the garbage collection are not set
+with the options @St{incremental} and @St{generational};
+instead, there is a new option @St{setparam} to that end.
+Moreover, there were some changes in the parameters themselves.
 }
 
 }
@@ -9277,9 +9306,10 @@ to signal the end of the dump.
 }
 
 @item{
-There were several changes in the parameters
-for the options @Lid{LUA_GCINC} and @Lid{LUA_GCGEN}
-of the function @Lid{lua_gc}.
+Parameters for the garbage collection are not set
+with the options @Lid{LUA_GCINC} and @Lid{LUA_GCGEN};
+instead, there is a new option @Lid{LUA_GCSETPARAM} to that end.
+Moreover, there were some changes in the parameters themselves.
 }
 
 }

testes/gc.lua

@@ -27,17 +27,20 @@ end
 
 -- test weird parameters to 'collectgarbage'
 do
+  collectgarbage("incremental")
+  local opause = collectgarbage("setparam", "pause", 100)
+  local ostepmul = collectgarbage("setparam", "stepmul", 100)
   local t = {0, 2, 10, 90, 500, 5000, 30000, 0x7ffffffe}
   for i = 1, #t do
-    local p = t[i]
+    collectgarbage("setparam", "pause", t[i])
     for j = 1, #t do
-      local m = t[j]
-      collectgarbage("incremental", p, m)
+      collectgarbage("setparam", "stepmul", t[j])
       collectgarbage("step")
     end
   end
   -- restore original parameters
-  collectgarbage("incremental", 200, 300)
+  collectgarbage("setparam", "pause", opause)
+  collectgarbage("setparam", "stepmul", ostepmul)
   collectgarbage()
 end
 

testes/gengc.lua

@@ -163,14 +163,15 @@ assert(collectgarbage'isrunning')
 
 
 do  print"testing stop-the-world collection"
-  collectgarbage("incremental", nil, 0)
+  local step = collectgarbage("setparam", "stepsize", 0);
+  collectgarbage("incremental")
 
   -- each step does a complete cycle
   assert(collectgarbage("step"))
   assert(collectgarbage("step"))
 
   -- back to default value
-  collectgarbage("incremental", nil, 200)
+  collectgarbage("setparam", "stepsize", step);
 end
 
 collectgarbage(oldmode)