#4322: High CPU usage during idle time due to GC
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Reporter: hesselink | Owner:
Type: bug | Status: new
Priority: normal | Component: Runtime System
Version: 6.12.3 | Keywords: idle GC
Testcase: | Blockedby:
Os: MacOS X | Blocking:
Architecture: x86 | Failure: Runtime performance bug
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We have a web application using happstack. It always used ~1% CPU, which
was fine. Recently, we started caching more things in memory, and CPU
usage during idle time rose to 15-30%. We eventually determined this was
due to the idle time GC (we compile with -threaded). Using +RTS -I2
removed the problem.
This is similar to #3408, except that that says it is fixed in 6.12, and
that the interval is set to 5s. The docs [1] still mention 0.3s, though,
and since changing it to 2s fixes our problem, it seems it's not 5s by
default.
It is difficult to attach a simple test case, but I can test things if
needed.
[1] http://www.haskell.org/ghc/docs/6.12.2/html/users_guide/runtime-
control.html#rts-options-gc
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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4322>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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