[Haskell-cafe] GHC Heap Profiler time axis

Mateusz Kowalczyk fuuzetsu at fuuzetsu.co.uk
Fri Dec 19 16:26:52 UTC 2014

On 12/19/2014 03:46 PM, Anton Dessiatov wrote:
> Hello, Haskell-Cafe!
> For the last 2 days I’m debugging something that looks like a space
> leak. My program is a rather long-running network service. When I
> first used heap profiler I was a bit confused with its output that
> showed that my program was running for only about 0.3-0.4 seconds
> when I launched it idling for about a minute.
> That was confusing enough for me to dig into GHC sources trying to
> figure out the reason behind this and I found that values of the
> sample times are taken from the mut_user_time function, which returns
> a time that process spent in user-mode code (outside the kernel)
> minus time spent on garbage collection.
> This introduces great amount of unpredictable non-linearity of the
> heap profile graph x axis, which I personally consider very
> counterintuitive.
> So my question is does anybody know why is it done this way? Wouldn’t
> it be better if x axis would just show a time elapsed since the
> process started?
> Kind regards, Anton.

ghc-user or ghc-devs lists may be more appropriate for this question.

I am eager to find out myself.

Mateusz K.

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