[commit: ghc] ghc-8.0: users_guide: More capabilities than processors considered harmful (10ba4f0)

[git at git.haskell.org]

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

On branch  : ghc-8.0
Link       : http://ghc.haskell.org/trac/ghc/changeset/10ba4f0a40dbf5f6bc47abd9ff294901ad222538/ghc

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

commit 10ba4f0a40dbf5f6bc47abd9ff294901ad222538
Author: Ben Gamari <bgamari.foss at gmail.com>
Date:   Tue Aug 30 17:05:25 2016 -0400

    users_guide: More capabilities than processors considered harmful
    
    Test Plan: None.
    
    Reviewers: austin, simonmar
    
    Reviewed By: simonmar
    
    Subscribers: thomie
    
    Differential Revision: https://phabricator.haskell.org/D2487
    
    (cherry picked from commit 28b71c55d057b780d92b351498ec611287dedbd4)


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10ba4f0a40dbf5f6bc47abd9ff294901ad222538
 docs/users_guide/using-concurrent.rst | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/docs/users_guide/using-concurrent.rst b/docs/users_guide/using-concurrent.rst
index c5179c7..676d094 100644
--- a/docs/users_guide/using-concurrent.rst
+++ b/docs/users_guide/using-concurrent.rst
@@ -136,7 +136,8 @@ RTS ``-N`` options.
 
     Be careful when using all the processors in your machine: if some of
     your processors are in use by other programs, this can actually harm
-    performance rather than improve it.
+    performance rather than improve it. Asking GHC to create more capabilities
+    than you have physical threads is almost always a bad idea.
 
     Setting ``-N`` also has the effect of enabling the parallel garbage
     collector (see :ref:`rts-options-gc`).