#2089: reading the package db is slow
---------------------------------------------+------------------------------
Reporter: duncan | Owner:
Type: compile-time performance bug | Status: new
Priority: normal | Component: Driver
Version: 6.8.2 | Severity: minor
Keywords: | Testcase:
Architecture: x86_64 (amd64) | Os: Multiple
---------------------------------------------+------------------------------
With a large number of registered packages it takes ages for ghc to read
the package db and it does this every time it is run so it starts to add
up.
I have a rather fast x86-64 machine and 160 registered packages. Here are
some timings:
{{{
$ time ghc-pkg list > /dev/null
user 0m1.164s
$ time ghc -c does-not-exist.c 2> /dev/null
real 0m0.612s
$ time hsc2hs does-exist.hsc --cflag=--version 2> /dev/null
user 0m0.572s
}}}
So since cabal configure involves running all of the above it starts to
take a while:
{{{
$ time cabal configure
Configuring cabal-install-0.4.3...
real 0m2.241s
user 0m1.916s
}}}
The obvious solution is to use a binary cache of the package db containing
the most commonly needed mappings like module name -> package etc.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2089>
GHC <http://www.haskell.org/ghc/>
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