On Thu, Apr 23, 2020 at 10:10:56PM +0000, Andrew Doran wrote: > This affects amd64, alpha and aarch64, but only 1 and 2 CPU systems so far. > Any more and it's still off by default. Only the default has changed so the > sysctl (vm.ubc_direct) still works for turning it on and off manually. > > This works great for me on amd64 but needs some tweaks to handle many CPUs. > I have some ideas on that one and hopefully will have something to try soon.
What are the risks of switching it on for > 2 CPUs? (With a LOCKDEBUG kernel on a 8-core ryzen 1700 for PR kern/55362, after days I'm at # dd if=/dev/zero obs=64k | progress -l 12884901888b dd of=/dev/rdk6 ibs=64k 8% |** | 544 GiB 2.18 MiB/s --:-- ETA which I think could be helped with ubc_direct. I don't wnat to increase the problem domain though.) Cheers, Patrick