On Wed, 10 Aug 2016, David Malcolm wrote: > Looks like inside a pop there's a lazy allocation of a map, and a > get_or_insert. Could this make -ftime-report have an impact on the > timing?
-ftime-report already has a great impact on timing because it adds a syscall on each timevar change (which happens thousands of times). It's possible to diminish that impact by using a time measuring facility that can go through just the vDSO on Linux (e.g. clock_gettime), but that wouldn't make split user/kernel timing available, and on old glibc versions you get clock_gettime only with -lrt. On a random translation unit of about 1800 sloc the impact of -ftime report is: w/o -ftime-report with -ftime-report real 0m0.456s real 0m0.544s user 0m0.447s user 0m0.464s sys 0m0.009s sys 0m0.079s Alexander
