Could you point out, aside from the large numbers of clients I mentioned (and the development overhead of implementing multi-process memory management code), what the article mentions is a primary drawback of using processes over threads?
> The overhead of cross-process context switches is inherently higher than switching between threads in the same process - and my suspicion is that that overhead will continue to increase. Once you have a significant number of connections we end up spending a lot of time in TLB misses, and that's inherent to the process model, because you can't share the TLB across processes.
Yes, that's per-client performance scaling ("significant number of connections"), which indicates a pooled connection model might mitigate most of the performance impact while allowing some core code to remain process-oriented (and thus, not rewritten).
pgbouncer is not transparent, you loose features, particularly when using the pooling mode actually allowing a larger number of active concurrent connections. Solving those issues is a lot easier with threads than with processes.
We're really talking about X-per-client as the primary reason to move away from processes, right?
So if you can get most of the benefit via pooling... why inherit the pain of porting?
Presumably latency jitter would be a difficult problem with pools, but it seems easier (and safer) than porting processes -> threads.
Disclaimer: High performance / low latency DB code is pretty far outside my wheelhouse.