Re: ticky/cc profiling and heap checks

18 Feb 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.

Cheers,
	Simon
...
On Mon, Feb 18, 2013 at 2:19 PM, Simon Marlow mailto:marlowsd@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