On Fri, Apr 07, 2017 at 05:20:31PM +0200, Peter Zijlstra wrote: > On Fri, Apr 07, 2017 at 06:47:43PM +0800, Jin Yao wrote: > > Perf already has support for disassembling the branch instruction > > and using the branch type for filtering. The patch just records > > the branch type in perf_branch_entry. > > > > Before recording, the patch converts the x86 branch classification > > to common branch classification and compute for checking if the > > branches cross 4K or 2MB areas. It's an approximate computing for > > crossing 4K page or 2MB page. > > The changelog is completely empty of rationale. Why do we care? > > Not having the binary is a very bad reason; you can't do much of > anything if that's missing.
It's a somewhat common situation with partially JITed code, if you don't have an agent. You can still do a lot of useful things. We found it useful to have this extra information during workload analysis. Forward conditionals and page crossing jumps are indications of frontend problems. -Andi
