Re: Incremental garbage collection ?
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- Subject: Re: Incremental garbage collection ?
- From: Roberto Ierusalimschy <roberto@...>
- Date: 2001年1月31日 10:12:16 -0200
> What happens is that periodically the PLC scan time jumps from 2-3
> milliseconds to 32 milliseconds which is unacceptable for us. We believe
> that it is the garbage collection that is kicking in [...]
Well, the first step is to be sure whether the problem is really GC. You
can set a GC tagmethod for tag nil:
lua_pushcfunction(L, f);
lua_settagmethod(L, LUA_TNIL, "gc");
After this code, function 'f' will be called everytime Lua does a GC
cicle.
If the problem is really GC, I don't think it would be easy to implement an
incremental garbage collector in Lua. But maybe you can solve your problem
in another way.
The API of Lua 4.0 gives you a good control over Lua GC. You can stop it,
force it, and check its internal state. So, if your application has some
"idle" time, you can use it to do a GC, and then you stop the GC during
the critical parts of your system. Something like this (untested code...):
/* busy time: freeze GC */
limit = lua_getgcthreshold(L); /* previous limit */
lua_setgcthreshold(L, 1000000); /* set limit to 1G */
/* idle time; check GC */
/* using more than 0.8 of the limit? */
if (lua_getgccount(L)/8 >= limit/10)
lua_setgcthreshold(L, 0); /* force a GC cicle */
You can also use some fixed value for 'limit', if you have an estimation
of how much memory Lua can use.
-- Roberto