On Fri, Mar 29, 2002 at 01:54:00AM -0500, Melvin Smith wrote: > At 10:30 PM 3/28/2002 -0800, Steve Fink wrote: > >When you call pmc_new, the init() routine is run before the PMC is > >anchored to the root set. This is a problem for things like > >aggregates, because they are likely to want to allocate a big Buffer > >during initialization. And disabling GC entirely just feels wrong -- > >especially with pmc_new_sized, it is very believable that this is a > >very good time to be collecting garbage. > > > >In short, it feels special-casey enough to me to warrant the following > >patch, which adds a new item to the root set for just this purpose. It > >could probably be better named. Dan, whaddaya think? > > I'd prefer to use a flag to make GC pass over the particular item so > it can be recursive, etc. Else you have to do something funky when > creating entities that create other entities.
Good point. > Just setting a bit upon entry, then clearing the bit after its > linked to the root set should do the trick. > > Isn't there already such a bit? I looked for one, but couldn't find anything. The live bit is for internal GC use only (and will get cleared at the beginning of a mark scan, so don't bother). The constant bit would work, except you'd have no way of detecting whether the init routine set the constant bit itself. Actually, there was a pair of bits that sounded perfect -- the reference count bits. Unfortunately, they're never examined. But they're probably the real answer. > Another alternative is a generic stack which you would push pointers > to pointers, so even if you triggered a GC run you'd still have the > correct pointer. Yes, that would be the simplest way to beef up the creating_pmc technique to handle your objection above, but it seems pretty complex compared to the bit technique. > I think its more efficient to just set/clear a flag, but stashing a > pointer to a pointer lets GC move it if it needs. ....and this is what the complexity would buy. :-) -- WM ISO JOB. http://foxglove.dnsalias.org/~sfink/job.html C, perl, networking, performance optimization, Java, XML.
