[GHC] #12181: Multi-threaded code on ARM64 GHC runtime doesn't use all available cores

[GHC]

#12181: Multi-threaded code on ARM64 GHC runtime doesn't use all available cores
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        Reporter:  varosi                   |                Owner:  (none)
            Type:  bug                      |               Status:  new
        Priority:  normal                   |            Milestone:
       Component:  Runtime System           |              Version:  7.10.3
      Resolution:                           |             Keywords:
Operating System:  Unknown/Multiple         |         Architecture:  arm
 Type of failure:  Runtime performance bug  |            Test Case:
      Blocked By:                           |             Blocking:
 Related Tickets:                           |  Differential Rev(s):
       Wiki Page:                           |
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Comment (by bgamari):

 At the moment there is no milestone meaning we aren't targetting any
 particular release for a fix. I will say that I'm not terribly keen on the
 idea of polling to get CPU information. I tend to agree with Reid that
 this is a distribution issue: bringing CPUs entirely offline for the sake
 of power management seems a bit crazy. Don't the Linux `cpufreq`,
 `cpuidle`, and clock management, and runtime PM subsystems exist precise
 to avoid this sort of heavy-weight power management?

 Why not just implement the RTS's `-N` logic yourself, but using at
 `_SC_NPROCESSORS_CONF` instead of `_SC_NPROCESSORS_ONLN`?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12181#comment:11>
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