[GHC] #9105: Profiling binary consumes CPU even when idle on Linux.

[GHC]

#9105: Profiling binary consumes CPU even when idle on Linux.
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        Reporter:  robinp            |                Owner:  bgamari
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Runtime System    |              Version:  7.8.2
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86
 Type of failure:  Runtime           |            Test Case:
  performance bug                    |
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1822
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"b01288d509b0f9e45f23ae48f2366f85f489089c/ghc" b01288d/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="b01288d509b0f9e45f23ae48f2366f85f489089c"
 rts: Disable tick timer unless really needed

 Trac #9105 notes significant CPU usage by an otherwise idle process when
 compiled with profiling. The reason for this is that we keep the tick
 timer active in the profiling RTS even if profiling wasn't requested at
 runtime.

 If the user requests any sort of profiling then we need to keep the
 timer active to ensure that samples are collected.

 Test Plan: Validate, check CPU usage, ensure profiling still works

 Reviewers: simonmar, austin

 Reviewed By: simonmar, austin

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1822

 GHC Trac Issues: #9105
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9105#comment:5>
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