[GHC] #9599: app runs 10 times faster when compiled with profilling information than without it

[GHC]

#9599: app runs 10 times faster when compiled with profilling information than
without it
-------------------------------------+-------------------------------------
       Reporter:  kgardas            |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  Compiler           |                 Version:  7.8.2
       Keywords:                     |        Operating System:  Solaris
   Architecture:  x86                |         Type of failure:  Runtime
     Difficulty:  Unknown            |  performance bug
     Blocked By:                     |               Test Case:
Related Tickets:                     |                Blocking:
                                     |  Differential Revisions:
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 Hello,
 I've found interesting application code which when compiled with
 {{{
 -O2 -threaded --make
 }}}
 runs 10 times slower than the same code compiled with
 {{{
 -O2 -threaded --make -prof -auto-all -caf-all -fforce-recomp
 }}}
 the application is compiled by GHC 7.8.2 on i386-solaris2 platform. The
 profiling application is then run as normal application, i.e. without +RTS
 -p.
 The application itself is my crude beginner Haskell code which takes
 Wikipedia dump (XML file) and tries wiki pages from there import into
 XWiki using REST API. It uses Data.Text package for lazy load of Wikipedia
 data, whole logic of selection of page/title/content is done on Data.Text
 and later saved into XPage which is using ByteString. The application also
 uses Simon Marlow's Async/async/wait code which is copied from Simon
 Marlow's Parallel and Concurrent Programming in Haskell
 http://chimera.labs.oreilly.com/books/1230000000929
 App attached.

 My question is, what to do with it to help finding the issue? E.g. I
 assume it's issue when profiling app is that much faster than common
 optimized app. For your information, optimized app takes 9m50s to upload
 1000 pages while profiled optimized app takes only 50s to upload the same
 amount of pages on my equipped with E5-2620 (2 GHz 6 core/12 threads xeon)
 Also the difference in time is that big that it's not caused by a noise in
 import of pages on XWiki side. I've tested several times of course.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9599>
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