[GHC] #13944: Introduce synchronized FFI

[GHC]

#13944: Introduce synchronized FFI
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        Reporter:  winter            |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by winter):

 I'm not sure if only the 10m runtimes were large enough to be meaningful,
 the problems is that for large files, we indeed spend more time on read
 and write instead of FFI scheduling, and unsafe FFI's blocking behaviour
 is indeed bad in this case.

 The different size of test is really supposed to test how different
 strategy react to each kind of workload, but i may have been failed to do
 that in that test though.

 FYI, currently in base we always do an unsafe read/write before call
 threadWaitRead/Write on *nix system, and since disk file never block, this
 is simply same as issue an unsafe call.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13944#comment:13>
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