slow execution of built executables on a Mac

Ben Gamari ben at
Sun Nov 11 03:10:35 UTC 2018

Richard Eisenberg <rae at> writes:

> OK. Well, I couldn't sample from Activity Monitor, because the
> processes came and went too quickly. But the terminal command `sample`
> takes a *name* as an argument, and so passing ghc-stage1 worked
> nicely. Samples were taken during rts_dist_HC calls.
Hmmm, it looks to me like all of these are from GHC waiting on various
things (e.g. _pthread_cond_wait, nanosleep, and pthread_join). It's
quite surprising that these operations are chewing through cycles in
kernel mode. I wonder how rapidly we are context switching. Perhaps we
are quickly jumping between kernel and user mode? Perhaps strace (or I
think the OS X equivalent is truss?) will shed some light?


- Ben
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