On Wed, Aug 19, 2020 at 09:16:59AM +0200, Christophe Leroy wrote: > I made a test with only the first patch of your series: That's definitely > the culprit. With only that patch applies, the duration is 6.64 seconds, > that's a 25% degradation. For the record: the first patch is: mem: remove duplicate ops for /dev/zero and /dev/null So these micro-optimizations matter at least for some popular benchmarks. It would be easy to drop, but that means we either: - can't support kernel_read/write on these files, which should not matter or - have to drop the check for both ops being present Al, what do you think?