#9321: Support for waiting on multiple MVars -------------------------------------+------------------------------------- Reporter: schyler | Owner: simonmar Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.3 Component: Runtime | Keywords: mvar System | Operating System: Unknown/Multiple Resolution: | Type of failure: None/Unknown Differential Revisions: | Test Case: Architecture: | Blocking: Unknown/Multiple | Difficulty: Unknown | Blocked By: | Related Tickets: | -------------------------------------+------------------------------------- Comment (by simonmar): I think it's really really hard to add support for multi-MVar operations. So I'm with Simon: we should put our efforts into improving STM instead. On the fairness point, MVar's fairness guarantee means that MVar actually performs quite badly under contention, due to the excessive number of context switches. Have you measured your application using both MVar and STM? STM transactions with only a few TVars perform quite well in my experience, and tend to outperform MVar under heavy contention. Nevertheless, if you want to go ahead with this, you'll need (a) a clear description of the desired semantics, and (b) a detailed implementation plan. I think you'll encounter lots of problems trying to do both of these. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9321#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler