Doug Hardie wrote:

If you did recompile it and it is behaving differently then it is probably because your program contains bugs in how it manages memory that happened to be working by accident with the old memory allocator. e.g. because you were making use of memory after it had been freed, but before the allocator returned it to some other malloc() call.


That is certainly possible. However, the program has worked under considerable load for many years with versions 3.7 to 6.2. Problems only occur with 7.0. The program is quite complex and big. It uses

The memory allocator was the same between 3.7 and 6.x - it only changed in 7.0. Your description looks like a use-after-free bug. Your application is in C, not C++, right?

probably hundreds of mallocs in a typical use. The problems only occur reasonably randomly and only under quite heavy load. The developer is looking into it, but the problem only occurs on FreeBSD 7.0, not any other Unix systems. In the meantime I am losing money because of it.

Some generic things to try:
- add debug flags to malloc.conf, especially "J", maybe "X" and "P" and see if anything abnormal comes up. If it does, the bug is in the program. - run it on an older version of FreeBSD with debugging flags (for the old malloc: "J", "X" and "Z"), also look for problems.
- link with an alternative malloc, there are several in ports
- link with a debugging malloc, try to see if there are bugs

Finally, there is no way to revert to the "old approach" because the new allocator is completely new; it allocates memory based on its own strategy. None of the malloc options affect the behaviour of correct programs (but some of them can help to improve performance, or to debug incorrect programs).

Not surprising but I seem to recall that when it was first introduced into stable that there was some discussion on how to make it look more like the old malloc. I couldn't find that via a search though.

You can never make it look like the old malloc - that was the point of introducing it. There could be a bug in the new malloc, but many complex programs are running fine on it so the chances are slim.

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