[GHC] #8224: Excessive system time -- new IO manager problem?

[GHC]

#8224: Excessive system time -- new IO manager problem?
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        Reporter:  rrnewton          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Runtime System    |              Version:  7.7
      Resolution:                    |             Keywords:  IO Manager,
                                     |  System Time
Operating System:  Linux             |         Architecture:  x86_64
 Type of failure:  Runtime           |  (amd64)
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9221             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by alkar):

 Hi, as a developer on 48-core machine, I upvote the issue. I can reproduce
 it with many programs, e.g. this trivial one:


 {{{
 #!bash
 $ cat x.hs
 main = getContents >>= print . length
 $ ghc -O2 -rtsopts -threaded x
 $ time head -c10MB /dev/zero | ./x
 10000000

 real    0m0.182s
 user    0m0.180s
 sys     0m0.012s
 $ time head -c10MB /dev/zero | ./x +RTS -N
 10000000

 real    0m1.782s
 user    0m45.183s
 sys     0m10.305s
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8224#comment:30>
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