On Thu, Jan 11, 2018 at 07:34:31PM +0000, Alan Cox wrote: > On Thu, 11 Jan 2018 13:26:01 -0600 > Josh Poimboeuf <jpoim...@redhat.com> wrote: > > > On Thu, Jan 11, 2018 at 08:19:35PM +0100, Olivier Galibert wrote: > > > Wouldn't the time taken by an easy syscall like getuid be a clear > > > indicator? > > > > I think only if you had a baseline measurement to compare against. > > getuid can also be cached by a smart libc. getppid() is what micro > benchmarks seem to favour.
I initially tried getpid() which I found to be cached by glibc, but I switched to write(-1, "a", 1) in the example in the cover letter and the test for 3 million runs roughly climbs from 200 ms to 900 ms under kvm (with PCID this time, I didn't retest without). Willy
