Per tag explicit garbage colection.
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- Subject: Per tag explicit garbage colection.
- From: Paul Hsieh <qed@...>
- Date: 2001年10月21日 15:01:40 -0700
As the subject says, I've implemented a per-tag explicit garbage collection. It is
my opinion that this kind of feature is necessary for applications that are
sensitive to resource usage on the C-side. Put in another way, it provides more
granularity into Lua's implicit garbage collection semantics from the explicit
malloc/free world of C. I'd like to know what people think of this, and whether or
not people think this, or something like it should go into a future version of Lua.
Should I also add this is a proposal on http://lua-users.org/wiki/?
I am currently using Lua 4.0 so I don't know what forward porting is required for
4.1, but in any event here are my additions:
To src/lgc.c I added:
-------------------------------------------------------------------
/*
* Extension to LUA's garbage collection system for user data
* Paul Hsieh
*/
void luaC_udatacollectgarbage (lua_State *L, int tag) {
TObject o;
TString *udata;
markall(L);
invalidaterefs(L); /* check unlocked references */
collectudata(L, 0);
ttype(&o) = LUA_TUSERDATA;
L->GCthreshold = 2*L->nblocks; /* avoid GC during tag methods */
while ((udata = L->TMtable[tag].collected) != NULL) {
L->TMtable[tag].collected = udata->nexthash; /* remove it from list */
tsvalue(&o) = udata;
callgcTM(L, &o);
luaM_free(L, udata);
}
checkMbuffer(L);
L->GCthreshold = 2*L->nblocks; /* set new threshold */
callgcTM(L, &luaO_nilobject);
}
-------------------------------------------------------------------
to src/lapi.c I added:
-------------------------------------------------------------------
/*
* Extension to LUA's garbage collection system for user data
* Paul Hsieh
*/
LUA_API void lua_udatacollectgarbage (lua_State *L, int tag) {
luaC_udatacollectgarbage (L, tag);
}
-------------------------------------------------------------------
to include/lua.h I added:
-------------------------------------------------------------------
/*
* Extension to LUA's garbage collection system for user data
* Paul Hsieh
*/
LUA_API void lua_udatacollectgarbage (lua_State *L, int tag);
-------------------------------------------------------------------
It appears to work as expected. However, just as a matter of good design, it might
make sense to perform per tagged userdata core garbage collection from a seperate
function that is callable both from luaC_udatacollectgarbage() and callgcTMudata().
--
Paul Hsieh
qed@pobox.com