Re: Problems freeing memory with Free

[Florian Weimer <fw@deneb.enyo.de>]

randhol+abuse@pvv.org (Preben Randhol) writes:

> I have made a double linked list which seems to preform correctly using
> a debugger. The problem however is that if I delete all the Nodes except
> the last and at the same time look at the programs memory usage with
> "top" under Linux, it reports the same amount of memory all the time. If
> it then delete the last node too, the memory suddenly drops down to the
> expected value (that is same as before the nodes were made). 

There's no error.  A typical implementation of a storage pool
retrieves memory in large chunks from the operating systems and
allocates several objects in each chunk.  When the objects are freed,
a chunk can only be returned to the operating system if all objects
which had been allocated in it before have been freed (unless you've
got a compacting garbage collector, but that's another story).

I think we discussed this phenomenon just a few months ago.