[GHC] #12896: Consider using compact regions in GHC itself to reduce GC overhead
#12896: Consider using compact regions in GHC itself to reduce GC overhead -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In make mode, GHC keeps a lot of in-memory data structures about modules it has built and interface files it has read. These data structures are long-lived and immutable (at least, per module/mutually recursive module group/package), so they may be candidates for storing in compact regions to reduce the work done by the GC. Potential problem: if we rely heavily on lazy evaluation in these structures for the purpose of avoiding work that will never be needed, then we can't store them in a compact region (since the contents of a compact region must be fully evaluated). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12896 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12896: Consider using compact regions in GHC itself to reduce GC overhead -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by niteria): * cc: niteria (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12896#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12896: Consider using compact regions in GHC itself to reduce GC overhead -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonmar): I actually tried using it for interface files, but it won't work (yet). We can't compact pinned memory, and FastString is implemented in terms of ByteString, which is backed by pinned memory. Perhaps we ought to special-case this somehow, because compacting things involving ByteString would be really useful - it would be possible but we have to adjust the address stored in the ByteString when we copy it. (or fix ByteString to use unpinned memory, which we want to do anyway, but that's harder). Also I'm not 100% sure that there aren't functions buried somewhere in ModIface, which also can't be compacted. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12896#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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