[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 have did some
 benchmarks[https://github.com/winterland1989/stdio/tree/newFD/bench/diskIO
 here], my conclusion is that under concurent disk I/O situations, safe FFI
 can cause a slow down up to 50%.

 The problem is if the disk is slow enough, or the file is not in page
 cache, then safe FFI may be a good choice. OTOH, if a blocking read
 doesn't take too much time, we'd better simply issue an unsafe read.

 I can't answer all the questions you're asking now though, i'm thinking
 for disk I/O a small thread pool maybe a better answer, since the I/O
 throughput will not increase or even downgrade when conncurrent number
 exceed a certain value. (for example, libuv do this).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13944#comment:11>
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