inconsistent back end bound values

[Stefano_C_2]

Hello,

In the attached screenshots VTune reports a back-end bound issue in the first 5 functions. When I expand the column to see the underlying category, some of them reveal no apparent issue (i.e. are not highlighted and the numeric value is equal to 0). I was wondering if it's just a bug or I should interpret the results somehow.

Thanks

[Stefano_C_2]

That happens if I select to show data as bars or numeric, under the categoy Unifilled pipeline slots, both Self and Total. (only Total is shown in the screenshots)

[Bernard]

It simply means that CPU front-end has ready to allocation uop(s) , but back-end(execution ports and execution units) cannot process those uops because of some circumstances like instruction latency or interdependencies.

By looking at screenshot highlighted function is 100% back end bound.

BTW it could be also some kind of bug because of inconsistency of the results.Highlighted function run for short period of time a few dozens of clock interrupt cycles maybe there is insufficient amount of collected data?

[Stefano_C_2]

iliyapolak wrote:

Highlighted function run for short period of time a few dozens of clock interrupt cycles maybe there is insufficient amount of collected data?

That was the problem. A longer run showed consistent results.

Thanks.

[Bernard]

You are welcome.