[DynInst_API:] Perturbation caused by instrumentation

[Marc BrÃnink <marc@xxxxxxxxx>]

Dear all,

I just started to look into perturbation caused by instrumentation.
To this end I measure the execution time of a function with and without 
instrumentation and compare the resulting distributions.
I attached 2 graphs:
a.pdf: execution without any instrumentation
b.pdf: execution with instrumentation

I instrument the entry point of a function and add a call to a 
different, empty function. The function is called at a single location. 
I was wondering whether anyone can make a good guess about why there is 
a plateau at 4e-7 in b.pdf
Setting any of the set* function to non-default values, e.g. switching 
off delayed parsing, did not change anything. The behaviour is very 
reproducible.
There might be quite a few things going on here. But maybe someone can 
make an educated guess and point me at the right direction?
Marc

Attachment: a.pdf
Description: Adobe PDF document

Attachment: b.pdf
Description: Adobe PDF document