> On Jan 29, 2020, at 5:36 AM, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > On Tue, Jan 28, 2020 at 02:07:10PM -0500, Qian Cai wrote: >> On Jan 28, 2020, at 12:47 PM, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: >>> The primary goal here is not finding regressions but having clearly >>> defined semantics of the page table accessors across architectures. x86 >>> and arm64 are a good starting point and other architectures will be >>> enabled as they are aligned to the same semantics. >> >> This still does not answer the fundamental question. If this test is >> simply inefficient to find bugs, > > Who said this is inefficient (other than you)? Inefficient of finding bugs. It said only found a bug or two in its lifetime? > >> who wants to spend time to use it regularly? > > Arch maintainers, mm maintainers introducing new macros or assuming > certain new semantics of the existing macros. > >> If this is just one off test that may get running once in a few years >> (when introducing a new arch), how does it justify the ongoing cost to >> maintain it? > > You are really missing the point. It's not only for a new arch but > changes to existing arch code. And if the arch code churn in this area > is relatively small, I'd expect a similarly small cost of maintaining > this test. > > If you only turn DEBUG_VM on once every few years, don't generalise this > to the rest of the kernel developers (as others pointed out, this test > is default y if DEBUG_VM). Quite the opposite, I am running DEBUG_VM almost daily for regression workload while I felt strongly this thing does not add any value mixing there. So, I would suggest to decouple this away from DEBUG_VM, and clearly document that this test is not something intended for automated regression workloads, so those people don’t need to waste time running this. > > Anyway, I think that's a pointless discussion, so not going to reply > further (unless you have technical content to add). > > -- > Catalin
