#16065: Stack squeezing during context switches makes for non-determinism in allocations -------------------------------------+------------------------------------- Reporter: sgraf | Owner: (none) Type: task | Status: new Priority: normal | Milestone: ⊥ Component: Runtime System | Version: 8.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #4450, #8861 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Old description:
As #4450 and #8611 show, stack squeezing in the RTS makes allocation numbers between two different runs of the same binary non-deterministic, because its effect is depending on when context switches are bound to happen.
A short-term solution might be to deactivate stack squeezing for vulnerable benchmarks with `+RTS -Z` like in Phab:D5460, but IMO a more elegant solution would be to only deactivate stack squeezing in `threadPause` calls that happen due to context switches. Would you agree?
New description: As #4450 and #8611 show, stack squeezing in the RTS makes allocation numbers between two different runs of the same binary non-deterministic, because its effect is depending on when context switches are bound to happen. A short-term solution might be to deactivate stack squeezing for vulnerable benchmarks with ~~`+RTS -Z`~~ `+RTS -V0` like in Phab:D5460, but IMO a more elegant solution would be to only deactivate stack squeezing in `threadPause` calls that happen due to context switches. Would you agree? -- Comment (by sgraf): Updated the patch for #8611 to reflect this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16065#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler