#3408: idle GC causes large CPU usage if run more frequently than 1 second
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Reporter: JeremyShaw | Owner:
Type: bug | Status: new
Priority: normal | Component: Runtime System
Version: 6.10.4 | Severity: normal
Keywords: idle GC | Testcase:
Os: Linux | Architecture: Unknown/Multiple
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I have a web server which exhibits unusual CPU usage. When it first starts
it loads a bunch of state from disk -- around 800MB. It then sits idle
consuming no CPU. If I make any request to the server, it starts using
30-60% of the CPU and never goes back down -- even if the request does not
interact with the state system at all.
If I disable idle GC, then the problem goes away. If I set idle GC time
using, {{{+RTS -I1}}}, the problem goes away. If I set it to, {{{+RTS
-I0.9999999}}}, then I see the CPU usage issue.
Setting the {{{+RTS -I1}}} option is sufficient for now, but the
documentation says I should report any weirdness.
I do not have a simple test case for this.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3408>
GHC <http://www.haskell.org/ghc/>
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