[GHC] #11134: Limit frequency of idle GCs
#11134: Limit frequency of idle GCs -------------------------------------+------------------------------------- Reporter: dcturner | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Runtime | Version: 7.10.2 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In a server process with a relatively large heap (100s of MB) serving regular but relatively infrequent requests (~1 per sec) the idle GC runs after essentially every request which turns out to be extremely expensive: switching it off takes us from ~30% CPU to ~0.3% CPU. It is certainly useful have the GC run when idle but running it *every* time the process goes idle isn't necessary. It doesn't work to increase the delay (e.g. say -I2) as then the idle GC would never run, because the requests are rather regular. I'd quite like to be able to say something of the form "do a GC if idle for at least 0.3s as long as the idle GC has not run in the last 120s" - where 120s is another option passed to the RTS. Does this sound like a reasonable idea? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11134 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11134: Limit frequency of idle GCs -------------------------------------+------------------------------------- Reporter: dcturner | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonmar): Yes, sounds like a good idea to me. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11134#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11134: Limit frequency of idle GCs -------------------------------------+------------------------------------- Reporter: dcturner | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by raichoo): That sounds really useful. I'm having a similar issue with a couple of Haskell processes on a production system. They are not draining that much CPU but they are increasing in numbers and "idling" more and more of the CPUs. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11134#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11134: Limit frequency of idle GCs -------------------------------------+------------------------------------- Reporter: dcturner | Owner: dcturner Type: feature request | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1930 Wiki Page: | -------------------------------------+------------------------------------- Changes (by thomie): * owner: => dcturner * differential: => Phab:D1930 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11134#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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