Em Ter, 2010-05-11 às 21:45 -0300, Daniel Ruoso escreveu: > The threading model topic still needs lots of thinking, so I decided to > try out some ideas.
After BrowserUK feedback and some more reading (including http://www.c2.com/cgi/wiki?MessagePassingConcurrency ) and links from there on, I decided to rewrite that ideas in a bit different model, but still with the same spirit. 0 - The idea is inspired by Erlang and the IO Language. Additionally to OS threads there are the "Coroutine Groups". 1 - No memory is shared between "Coroutine Groups", so no locking is necessary. 2 - A value and a coroutine always belong to a "Coroutine Group", which should be assigned to a single OS thread, thus naturally implementing synchronized access to data. 3 - The interpreter implements a scheduler, which will pick one of the "waiting" coroutines that belong to the groups assined to the current thread. The scheduler may also suspend a coroutine in order to implement time-sharing. The scheduler should support "blocking" states in the coroutines. 4 - When comparing to Perl 5, each coroutine is an ithread, but memory is shared between all the coroutines in the same group, given that they will always run in the same OS thread. 5 - When a coroutine group is created, it is assigned to one OS thread, the interpreter might decide to create new OS threads as necessary, it might optionally implement one OS thread per "coroutine group". 6 - In order to implement inter-coroutine-group communication, there are: 6.1 - A "MessageQueue" works just like an Unix Pipe, it looks like a slurpy array. It has a configurable buffer size and coroutines might block when trying to read and/or write to it. 6.2 - A "RemoteInvocation" is an object that has a identifier, a capture (which might, optionally, point to a "MessageQueue" as input) and another "MessageQueue" to be used as output. New coroutines are created in the target group to execute that invocation. 6.3 - An "InvocationQueue" is a special type of "MessageQueue" that accepts only "RemoteInvocation" objects. 6.4 - A "RemoteValue" is an object that proxies requests to another coroutine group through a "RemoteInvocation". 7 - The coroutine group boundary is drawn by language constructs such as async, the feed operator, junctions, hyper operators. 8 - A value might have its ownership transferred to another group if it can be detected that this value is in use only for that invocation or return value, in order to reduce the amount of "RemoteInvocation"s. 9 - A value might do a special "ThreadSafe" role if it is thread-safe (such as implementing bindings to thread-safe native libraries) In which case it is sent as-is to a different group. 10 - A value might do a special "ThreadCloneable" role if it should be cloned instead of being proxied through a "RemoteValue" when sent in a "RemoteInvocation". 11 - The "MessageQueue" notifies the scheduler whenever new data is available in that queue so the target coroutine might be raised. 12 - Exception handling gets a bit hairy, since exceptions might only be raised at the calling scope when the value is consumed. 13 - List assignment and Sink context might result in synchronized behavior. comments are appreciated... daniel
