Threadscope reporting that nothing is happening (MUT or GC) for ~2 seconds

Patrick Palka patrick at
Tue Jul 30 22:22:34 CEST 2013

Mystery solved -- the gap is likely the RTS waiting on an external process
(the linker) to exit.

On Tue, Jul 30, 2013 at 3:34 PM, Patrick Palka <patrick at> wrote:

> Hi,
> I'm analyzing the performance of my parallel --make branch of GHC (
> if anyone is interested)
> by compiling the Cabal repository in parallel, using two capabilities.
> I'm seeing very strange results from Threadscope: at some point during the
> compile, absolutely no work is being performed on any HEC for about 2
> seconds. How do I interpret this kind of behavior? What does it mean?
> Relevant screenshot:
> Patrick
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