Simon Jakobi pushed to branch wip/sjakobi/T27602 at Glasgow Haskell Compiler / GHC

Commits:

• a4ddab82
  by Simon Jakobi at 2026-08-15T11:54:49+02:00

  DEMO: Tighten T9675 residency tolerance (do not merge)
  
  Revert the T4830 regression from the previous demo commit; T4830's
  'bytes allocated' turns out to be fully deterministic across CI
  samples, so it cannot show a spread.
  
  Instead tighten T9675's residency tolerance from 15% to 2%: its
  peak_megabytes_allocated jitters by up to ~12% between runs of the
  same commit, so with a multi-sample baseline the natural jitter
  fails the window and the new sample-spread output shows a baseline
  built from genuinely disagreeing samples.
  
  Context: #27602
  Assisted-by: Claude Fable 5
  

1 changed file:

• testsuite/tests/perf/compiler/all.T

Changes:

 test('T9675',

      [ only_ways(['optasm']),

-       collect_compiler_residency(15),

+       # Demo-only: tightened from 15 so natural residency jitter fails.

+       collect_compiler_residency(2),

        collect_compiler_stats('bytes allocated',2),

       ],

      compile,