Perf regression: ghc --make: add nicer names to RTS threads (threaded IO manager, make workers) (f686682)

[Joachim Breitner]

Hi,

the attached commit seems to have regressed the scs nofib benchmark by
~3%:
http://ghcspeed-nomeata.rhcloud.com/timeline/?ben=nofib/time/scs&env=1#/?exe=2&base=2+68&ben=nofib/time/scs&env=1&revs=50&equid=on

The graph unfortunately is in the wrong order, as the tool gets confused
by timezones and by commits with identical CommitDate, e.g. due to
rebasing. This needs to be fixed, I manually verified that the commit
below is the first that shows the above-noise-level-increase of runtime.

(Other benchmarks seem to be unaffected.)

Is this regression expected and intended or unexpected? Is it fixable?
Or is is this simply inexplicable?



Thanks,
Joachim


Am Montag, den 04.08.2014, 13:13 +0000 schrieb git at git.haskell.org:
> Repository : ssh://git@git.haskell.org/ghc
> 
> On branch  : master
> Link       : http://ghc.haskell.org/trac/ghc/changeset/f6866824ce5cdf5359f0cad78c49d65f6d43af12/ghc
> 
> >---------------------------------------------------------------
> 
> commit f6866824ce5cdf5359f0cad78c49d65f6d43af12
> Author: Sergei Trofimovich <slyfox at gentoo.org>
> Date:   Mon Aug 4 08:10:33 2014 -0500
> 
>     ghc --make: add nicer names to RTS threads (threaded IO manager, make workers)
>     
>     Summary:
>     The patch names most of RTS threads
>     and ghc (the tool) threads.
>     
>     It makes nicer debug and eventlog output for ghc itself.
>     
>     Signed-off-by: Sergei Trofimovich <slyfox at gentoo.org>
>     
>     Test Plan: ran debugged ghc under '+RTS -Ds'
>     
>     Reviewers: simonmar, austin
>     
>     Reviewed By: austin
>     
>     Subscribers: phaskell, simonmar, relrod, ezyang, carter
>     
>     Differential Revision: https://phabricator.haskell.org/D101
> 
> 
> >---------------------------------------------------------------
> 
> f6866824ce5cdf5359f0cad78c49d65f6d43af12
>  compiler/main/GhcMake.hs           | 14 ++++++++++++++
>  libraries/base/GHC/Event/Thread.hs |  8 ++++++--
>  2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/compiler/main/GhcMake.hs b/compiler/main/GhcMake.hs
> index 33f163c..0c63203 100644
> --- a/compiler/main/GhcMake.hs
> +++ b/compiler/main/GhcMake.hs
> @@ -63,6 +63,7 @@ import qualified Data.Set as Set
>  import qualified FiniteMap as Map ( insertListWith )
>  
>  import Control.Concurrent ( forkIOWithUnmask, killThread )
> +import qualified GHC.Conc as CC
>  import Control.Concurrent.MVar
>  import Control.Concurrent.QSem
>  import Control.Exception
> @@ -80,6 +81,11 @@ import System.IO.Error  ( isDoesNotExistError )
>  
>  import GHC.Conc ( getNumProcessors, getNumCapabilities, setNumCapabilities )
>  
> +label_self :: String -> IO ()
> +label_self thread_name = do
> +    self_tid <- CC.myThreadId
> +    CC.labelThread self_tid thread_name
> +
>  -- -----------------------------------------------------------------------------
>  -- Loading the program
>  
> @@ -744,10 +750,18 @@ parUpsweep n_jobs old_hpt stable_mods cleanup sccs = do
>                           | ((ms,mvar,_),idx) <- comp_graph_w_idx ]
>  
> 
> +    liftIO $ label_self "main --make thread"
>      -- For each module in the module graph, spawn a worker thread that will
>      -- compile this module.
>      let { spawnWorkers = forM comp_graph_w_idx $ \((mod,!mvar,!log_queue),!mod_idx) ->
>              forkIOWithUnmask $ \unmask -> do
> +                liftIO $ label_self $ unwords
> +                    [ "worker --make thread"
> +                    , "for module"
> +                    , show (moduleNameString (ms_mod_name mod))
> +                    , "number"
> +                    , show mod_idx
> +                    ]
>                  -- Replace the default log_action with one that writes each
>                  -- message to the module's log_queue. The main thread will
>                  -- deal with synchronously printing these messages.
> diff --git a/libraries/base/GHC/Event/Thread.hs b/libraries/base/GHC/Event/Thread.hs
> index 6e991bf..dcfa32a 100644
> --- a/libraries/base/GHC/Event/Thread.hs
> +++ b/libraries/base/GHC/Event/Thread.hs
> @@ -39,6 +39,7 @@ import GHC.Event.Manager (Event, EventManager, evtRead, evtWrite, loop,
>  import qualified GHC.Event.Manager as M
>  import qualified GHC.Event.TimerManager as TM
>  import GHC.Num ((-), (+))
> +import GHC.Show (showSignedInt)
>  import System.IO.Unsafe (unsafePerformIO)
>  import System.Posix.Types (Fd)
>  
> @@ -244,11 +245,14 @@ startIOManagerThreads =
>      forM_ [0..high] (startIOManagerThread eventManagerArray)
>      writeIORef numEnabledEventManagers (high+1)
>  
> +show_int :: Int -> String
> +show_int i = showSignedInt 0 i ""
> +
>  restartPollLoop :: EventManager -> Int -> IO ThreadId
>  restartPollLoop mgr i = do
>    M.release mgr
>    !t <- forkOn i $ loop mgr
> -  labelThread t "IOManager"
> +  labelThread t ("IOManager on cap " ++ show_int i)
>    return t
>  
>  startIOManagerThread :: IOArray Int (Maybe (ThreadId, EventManager))
> @@ -258,7 +262,7 @@ startIOManagerThread eventManagerArray i = do
>    let create = do
>          !mgr <- new True
>          !t <- forkOn i $ loop mgr
> -        labelThread t "IOManager"
> +        labelThread t ("IOManager on cap " ++ show_int i)
>          writeIOArray eventManagerArray i (Just (t,mgr))
>    old <- readIOArray eventManagerArray i
>    case old of
> 
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-- 
Joachim “nomeata” Breitner
  mail at joachim-breitner.de • http://www.joachim-breitner.de/
  Jabber: nomeata at joachim-breitner.de  • GPG-Key: 0xF0FBF51F
  Debian Developer: nomeata at debian.org

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