ticky/cc profiling and heap checks

Simon Marlow marlowsd at gmail.com
Mon Feb 18 21:10:41 CET 2013

On 18/02/13 17:38, Nicolas Frisby wrote:
> Moving all ticky bumps after the heapcheck did prevent the wiggling I
> noticed.
> Could you also weigh in on the location of the cost centre profiling
> entries?

The cost centre bumps should definitely be after the heap check too.


> On Mon, Feb 18, 2013 at 2:19 PM, Simon Marlow <marlowsd at gmail.com
> <mailto:marlowsd at gmail.com>> wrote:
>     On 16/02/13 16:32, Nicolas Frisby wrote:
>         I noticed some suspicious wiggling in my ticky reports' entry
>         counts.
>         SPJ suggested they were due to the counter ticking before the heap
>         check: if it fails, then it ticks again when we re-enter after the
>         stg_gc function does its thing.
>         After looking into it a bit further, I have a couple questions.
>         Here's
>         what I found.
>             * for functions (StgCmmBind.closureCodeBody), tickyEnterFun and
>         enterCostCentreFun are before the heap check
>             * for thunks (StgCmmBind.thunkCode), tickyEnterThunk is
>         before the
>         heap check and enterCostCentreThunk is after.
>         Questions:
>             * Does any object to me moving both ticky counters after the
>         heap check?
>             * Is there a reason the two cost centre profiling entries are on
>         opposite sides of the heap check?
>     It sounds wrong to me.  If you could clean this up that would be
>     great.  These counters should never be bumped before the heap check,
>     because if the heap check fails then the bumps will happen twice.
>     Cheers,
>              Simon

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