#15414: Why both gen and gen_no in bdescr? -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.1 Component: Runtime | Version: 8.4.3 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Block descriptors currently contain both `gen` (a `generation *`) and `gen_no` (a `uint16_t, which is `gen->no` cached). I wonder whether it would be worthwhile to drop the former and always use `generations[bd->gen_no]`. Afterall, this would save an entire word per descriptor which may improve our caches' coverage of the bdescr region appreciably. Presumably the `generations` array would be hot enough to stay in cache in such a scheme, so I would guess that the cost would be small-ish. Simon, have you measured this in the past? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15414 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler