On Tue, Aug 18, 2020 at 07:46:22PM +0200, Christophe Leroy wrote: > I gave it a go on my powerpc mpc832x. I tested it on top of my newest > series that reworks the 32 bits signal handlers (see > https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=196278) with > the microbenchmark test used is that series. > > With KUAP activated, on top of signal32 rework, performance is boosted as > system time for the microbenchmark goes from 1.73s down to 1.56s, that is > 10% quicker > > Surprisingly, with the kernel as is today without my signal's series, your > series degrades performance slightly (from 2.55s to 2.64s ie 3.5% slower). > > > I also observe, in both cases, a degradation on > > dd if=/dev/zero of=/dev/null count=1M > > Without your series, it runs in 5.29 seconds. > With your series, it runs in 5.82 seconds, that is 10% more time. That's pretty strage, I wonder if some kernel text cache line effects come into play here? The kernel access side is only used in slow path code, so it should not make a difference, and the uaccess code is simplified and should be (marginally) faster. Btw, was this with the __{get,put}_user_allowed cockup that you noticed fixed?
