[boost] [pool] future directions

From: Michael Gopshtein (mgopshtein_at_[hidden])
Date: 2007-05-07 17:13:32

According to documentation to "Pool" library, it is intended to be used 
"when there is a lot of allocation and deallocation of small objects".

In our product we also use such pool for allocation of "normal" - heavier 
objects. In such case we can't benefit from significant improvement in 
memory consumption per object (overhead of malloc's internal structure 
relative to used size of the object), but the allocations themselves are 
much more efficient.

Additional advantage is memory fragmentation - all objects in the pool 
reside in continuous memory blocks.

The main problem with such usage is, in our case, that the pool never 
"returns" memory to the system, unless it's released. For example, if I use 
the pool for allocation of Event objects, and at some point of time I had 
10000 concurrent events, the pool will occupy all that memory while the 
process is alive, even if for most of the time I use a small portion of it.

As a solution I was thinking about adding a "defragment" function to memory 
pool, which will compact it by moving live objects to free cells at the 
"beginning" of the pool. Such feature can be implemented with help of 
additional "index" table of pointers. Of cause, instead of returning pointer 
to allocated object, the pool will return a wrapper object, actually 
pointing to that index table (for which separate "classical" pool can be 
used).

So, the first question is: do you think such feature will be helpful?

If yes - please share your thoughts regarding suggested and/or other 
implementations?

Michael