On Fri, 11 Oct 2019, Dmitry Safonov wrote: > We wrote two small benchmarks. The first one gettime_perf.c calls > clock_gettime() in a loop for 3 seconds. It shows us performance with > a hot CPU cache (more clock_gettime() cycles - the better): > > | before | CONFIG_TIME_NS=n | host | inside timens > -------------------------------------------------------------- > | 153242367 | 153567617 | 150933203 | 139310914 > | 153324800 | 153115132 | 150919828 | 139299761 > | 153125401 | 153686868 | 150930471 | 139273917 > | 153399355 | 153694866 | 151083410 | 139286081 > | 153489417 | 153739716 | 150997262 | 139146403 > | 153494270 | 153724332 | 150035651 | 138835612 > ----------------------------------------------------------- > avg | 153345935 | 153588088 | 150816637 | 139192114 > diff % | 100 | 100.1 | 98.3 | 90.7 That host 98.3% number is weird and does not match the tests I did with the fallback code I provided you. On my limited testing that fallback hidden in the slowpath did not show any difference to the TIME_NS=n case when not inside a time namespace. Thanks, tglx
