On Thu, Jan 11, 2018 at 01:28:18PM -0800, Linus Torvalds wrote: > The traditional fast system call to test is getppid(). > > write() goes through a lot more code.
Just tried getppid() now, it's relatively similar (slightly slower than write(-1) though, maybe that one aborts very early) : PTI=on : 920ms for 3 million calls PTI=off (prctl) : 230ms for 3 million calls PTI=off (boot) : 215ms for 3 million calls The small difference between the last two very likely comes from the few instructions avoided thanks to the alternatives when pti=off is used at boot. So yes here it's trivial to tell if it's on or off :-) Willy
