On 24/10/2013 22:27, Quoth Marat Abrarov:
I actually ended up abandoning Asio and rolling my own threadqueue (I didn't want any of the socket-related stuff so this wasn't as big a job as it sounds). Mine isn't fully-baked yet (and it's Windows-only for the moment) and I'm not sure I'd want to show it off either, but on the upside most of the guts are entirely lock-free (though not wait-free, since it's based on Boost.LockFree's queue).
Asio at Windows uses IOCP (default settings, using asio::io_service for task scheduling) and that is the (theoretical) reason of better thread scheduling for the Asio-based thread pool. Sometimes it's really visible.
It's also full of mutexes though, which is why it didn't work out for me. (Note that I was using Boost 1.53 when testing Asio; maybe this has changed in future versions, although I heard that 1.54 picked up a bug in the IOCP reactor.) I'm not sure exactly which lock triggered the slow path (my logging was only sufficient to show that it was one of the ones inside Asio, but not which one). But as the prior email said, given reuse of strand implementations between supposedly independent strands, that seems like a likely candidate. (Though it didn't take long for the latency spikes to manifest -- typically they'd start after a couple of minutes and then recur roughly every 10-30 seconds.) My implementation also uses IOCP for the io_service equivalent but without the dispatch queue mutexes that Asio uses. The Boost.LockFree queue is used mostly for the io_strand and object_handle equivalents (and even then it's only used by the latter to support multiple concurrent waiters, which I didn't end up needing). (The strand, of course, is still blocking in the execution path but not in the posting path.) I haven't done a head-to-head benchmark on each (and it wouldn't surprise me if Asio were faster than mine for many loads -- and it's definitely more flexible than I made mine) but so far my one is doing at least as well as Asio on production loads but without the latency spikes from the locks. Still very early days yet though.