[GHC] #12758: Bring sanity to our performance testsuite

[GHC]

#12758: Bring sanity to our performance testsuite
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        Reporter:  bgamari           |                Owner:
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Test Suite        |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Description changed by bgamari:

@@ -13,1 +13,5 @@
-  *
+  * We replace the existing `compiler_stats_num_field` test modifier with
+ an implementation that dumps performance metrics to a CSV file
+  * Introduce a tool to compare this CSV file to metrics associated with a
+ ancestor commit via `git notes`
+  * The tool would also be able to add notes

New description:

 The GHC testsuite's performance tests tends to be a constant source of
 busy-work as it requires that contributors manually bump performance
 numbers and propagate these changes across platforms. Moreover, the
 testsuite is poor at noticing performance regressions due to false
 positive failures (due to spurious environmental differences) and false
 negatives (due to the rather generous acceptance windows that many tests
 have).

 Joachim and I briefly discussed this at Hac Phi and came up with the
 following proposal:

  * We rip expected performance numbers out of the `.T` files
  * We replace the existing `compiler_stats_num_field` test modifier with
 an implementation that dumps performance metrics to a CSV file
  * Introduce a tool to compare this CSV file to metrics associated with a
 ancestor commit via `git notes`
  * The tool would also be able to add notes

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12758#comment:1>
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