Re: Time to heat up the new module discussion

[Miguel de Icaza <miguel ximian com>]

Hello,

> >> so in other words it will spike every now and again EG if under Boehm GC 
> >> I have 50MB heap then in compacting mode its going to spike from 50 to 
> >> 100+ MB (how much higher depends on the no. of generations you have and 
> >> how incremental it is of course)
> > 
> > Yes, but the spike is not 2x the memory you have allocated.  The spike
> > is the size of the nursery (512k).
> 
> Sure for young generation collections but "major collections"  will be 
> 2x the allocated memory as they must include the older generations as 
> well as the nursery. (thats pretty much what the page link you gave says 
> unless I have misinterpreted it?)

The reason to perform a major collection would be to release some of the
resources there (otherwise a new block would be allocated).

So the new block allocated tends to be smaller than the sum of the
existing memory sections, as it only accounts for live objects, not live
objects plus dead objects.

> So we will see a doubling in size spike every now and again (it is after 
> all one of the main disadvantages common to *all* copying collectors so 
> no need to panic!)

That is the worst case scenario, yes.

Miguel.