#8400: Migrate the RTS to use libuv (or libev, or libevent) -------------------------------------+------------------------------------- Reporter: schyler | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Runtime System | Version: Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: 635, 7353 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by winter): Here's my analysis on the allocate and performance difference: Mio's centre data structure is a fixed sized(32) stripped int-table(using grow only buckets), it maps fd to its callback function. The bucket usually is quite full since fd numbers follow the least unused rule. My libuv binding's centre data structure is variadic size(capatibily number) stripped int-table(also using grow only buckets), it map a range limited *slot* to a `MVar`. It actually works like a per capatibily stable pointer table: we keep a free list of slot waiting to be assigned, and during GC the int-table is evacuated. So mio have to allocate extra callback closure, even it's usually just a `putMVar`, but libuv doesn't: it simply use slots from eventloop to unblock those `MVar`s. Theoretically mio is more flexible since you can do pretty much anything inside callback, but in practise this's not a problem for libuv: after we unblock the blocking thread, it can do anything it want to, too. I plan to optimize the `MVar` table further using `primitive` 's `UnliftedArray` trick: it use `ArrayArray#` to directly save `MVar#` in packed memory. It will cut the GC time spending on the table(which is already very low) half. But i can't see how this optimization work out for mio. Another direction to go is to optimize our stable pointer's implementation and use the new `try_put_mvar` in 8.2. But I'm afraid it would not be as fast as my current version since current version is optimizied for libuv's call convention: provide buffers and handles, then wait for callbacks. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8400#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler