Share memory between channels

[gavin-norman-sociomantic]

(AKA "Kombischlange".)

At present, there is a very large overhead per channel: a large, fixed-size, in-memory queue is allocated, even though most of the channels are empty most of the time. It should be possible to find a way to minimise this unused memory.

[gavin-norman-sociomantic]

One proposal for a system with greatly reduced per-channel overhead would be to use a shared memory pool, rather than one per channel. This could work something like the following:

• For each channel, a queue of pointers to records is maintained.
• When a record arrives, it is copied into a malloced buffer.
• A pointer to the record's buffer is pushed to that channel's queue.
• When a record is popped from memory, the buffer is simply freed and the pointer removed from the per-channel queue.

The per-channel queue of pointers has a limited size, both in terms of the number of items it may contain and in terms of the combined size in memory of the pointed-to records. In this way, the overhead per channel is reduced from a chunk of memory to store the actual records to a chunk of memory used to store a list of pointers to records, which could be significantly smaller.