> > Don't use it. It's misleading on a out-of-order CPU because you don't > > know if it's actually limiting anything. > > > > If you want useful bottleneck data use --topdown. > > So running again, this time with the below params, I got this output > where all the right most column is colored red. I wonder what can be > said on the amount/ratio of stalls for this app - if you can maybe recommend > some posts of yours to better understand that, I saw some comment in the > perf-stat man page and some lwn article but wasn't really able to figure it > out.
TopDown determines what limits the execution the most. The application is mostly backend bound (55-72%). This can be either memory issues (more common), or sometimes also execution issues. Standard perf doesn't support a further break down beyond these high level categories, but there are alternative tools that do (e.g. mine is "toplev" in https://github.com/andikleen/pmu-tools or VTune) Some references on TopDown: https://github.com/andikleen/pmu-tools/wiki/toplev-manual http://bit.ly/tma-ispass14 The tools above would also allow you to sample where the stalls are occuring. -Andi
