Improve performance of -profile by factor of 10

[Walter Bright]

On 3/25/2013 7:26 PM, Vladimir Panteleev wrote:
> On Monday, 25 March 2013 at 23:52:26 UTC, Walter Bright wrote:
>> On 3/25/2013 4:22 PM, Vladimir Panteleev wrote:
>>> The disadvantages of a polling profiler are:
>>
>> 4. not getting the fan in / fan out data.
>
> It is assembled from collected stack frames (assuming I understood the term
> correctly).

While you can get the caller (after all, debuggers do it), it can be arbitrarily 
costly (in terms of execution speed) to do so, which can negate many of the 
advantages of a probing profiler. The ones I've seen didn't bother to do it.

Fan in/out is very useful because the most effective optimization is to not call 
the time consuming functions, and this path information enables you to figure 
out where you don't really need to call it.