Re: [TCLCORE] Coroutines in HEAD

[Donal K. F. <don...@ma...>]

miguel sofer wrote:
> Scenario: webserver on a multicore cpu, one-coroutine-per-session. Ie, maintain 
> session state in the coro's local vars (as opposed to hitting a database or 
> something equivalent).
> 
> The way it is today, you may run as many threads as you have cores (or a bit 
> more), and allocate user sessions to the threads on creation in order to balance 
> the load. But once created, a session has to be resumed in the same thread each 
> time a new request comes in.
> 
> If the coros could be resumed in any thread, you could balance your load 
> dynamically - each time a request comes in.

This is only valuable when you are running a workload where the service
cost of a single session varies widely. If the cost of serving a single
client is fairly uniform, you get good enough load balancing from just
using a thread pool.

The down-side of relocating things across threads is that it makes
memory management *much* nastier, and introduces a whole bunch of hot
global locks. Don't go there, please!

Donal.