I've got perf failures on Linux 64-bit on ghc-7.8 (and master too, I think). Please take a look. Unexpected results from: TEST="T4801 T3064 T5837 T6048" OVERALL SUMMARY for test run started at Thu Apr 10 15:33:27 2014 PDT 0:02:52 spent to go through 3920 total tests, which gave rise to 12853 test cases, of which 9274 were skipped 26 had missing libraries 3491 expected passes 58 expected failures 0 caused framework failures 0 unexpected passes 4 unexpected failures Unexpected failures: perf/compiler T3064 [stat not good enough] (normal) perf/compiler T4801 [stat not good enough] (normal) perf/compiler T5837 [stat not good enough] (normal) perf/compiler T6048 [stat not good enough] (optasm)