[commit: ghc] wip/nfs-locking: Disable parallel garbage collection (#385) (57cfa03)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/nfs-locking
Link       : http://ghc.haskell.org/trac/ghc/changeset/57cfa03c23047bb0c731428e97ca716d9a1cf312/ghc

>---------------------------------------------------------------

commit 57cfa03c23047bb0c731428e97ca716d9a1cf312
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Sat Jul 29 06:28:14 2017 -0400

    Disable parallel garbage collection (#385)
    
    This brings productivity from roughly 40% to 95%. With parallel GC we generally
    spend much of our time synchronizing between the GC threads and relatively
    little time doing productive work.


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57cfa03c23047bb0c731428e97ca716d9a1cf312
 hadrian.cabal | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/hadrian.cabal b/hadrian.cabal
index 4eb43db..af5fd6c 100644
--- a/hadrian.cabal
+++ b/hadrian.cabal
@@ -133,5 +133,11 @@ executable hadrian
                        , happy >= 1.19.4
     ghc-options:         -Wall
                          -fno-warn-name-shadowing
-                         -rtsopts -with-rtsopts=-I0
+                         -rtsopts
+                         -- Disable idle GC to avoid redundant GCs while waiting
+                         -- for external processes
+                         -with-rtsopts=-I0
+                         -- Don't use parallel GC as the synchronization time tends to eat any
+                         -- benefit.
+                         -with-rtsopts=-qg0
                          -threaded