[Haskell-cafe] SMP parallelism increasing GC time dramatically

Tom Thorne thomas.thorne21 at gmail.com
Thu Oct 6 14:56:54 CEST 2011

I'm trying to narrow it down so that I can submit a meaningful bug report,
and it seems to be something to do with switching off parallel GC using -qg,
whilst also passing -Nx.

Are there any known issues with this that people are aware of? At the moment
I am using the latest haskell platform release on arch.

I'd like to give 7.2 a try in case that fixes it, but I'm using rather a lot
of libraries (hmatrix, fclabels, random fu) and I don't know how to install
them for multiple ghc versions

On Wed, Oct 5, 2011 at 10:43 PM, Johan Tibell <johan.tibell at gmail.com>wrote:

> On Wed, Oct 5, 2011 at 2:37 PM, Tom Thorne <thomas.thorne21 at gmail.com>wrote:
>> The only problem is that now I am getting random occasional segmentation
>> faults that I was not been getting before, and once got a message saying:
>> Main: schedule: re-entered unsafely
>> Perhaps a 'foreign import unsafe' should be 'safe'?
>> I think this may be something to do with creating a lot of sparks though,
>> since this occurs whether I have the parallel GC on or not.
> Unless you (or some library you're using) is doing what the error message
> says then you should file a GHC bug here:
> http://hackage.haskell.org/trac/ghc/
> -- Johan
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