On Fri, Mar 11, 2022 at 06:15:00PM -0500, Steven Rostedt wrote: > On Fri, 11 Mar 2022 10:13:28 -0800 > Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx> wrote: > > > Is that true as well for the user process that has this mapped? Will the > > user process virtual memory that maps to this ever page it out? I > > believe that was the concern. My understanding is by reserving in > > kernel, even though it won't page out on that side, marks the user side > > entry to not let it page out. > > My memory of the purpose of SetPageReserve() is a bit fuzzy, and there's > not much use of it in the kernel. Just a hand full. I'll try to investigate > it some more. > OK, you know more than I, so hopefully we can land on if we really need it or not. For now I've left it in. > > > > The other thing is that this patch applied to 5.10.X on ARM64 does not > > appear to hit this. Is it some weird interaction with something else or > > was 5.10.X just getting lucky? > > Perhaps it's because you allocated the page with kzalloc and not just > getting a page directly? > Yeah, I think so too. I was able to repro locally and validate that using alloc_pages directly fixes this by setting DEBUG_VM_PGFLAGS=y. I've posted a patch for this: https://lore.kernel.org/linux-trace-devel/20220311223028.1865-1-beaub@xxxxxxxxxxxxxxxxxxx/ > Again, my knowledge in this area is lacking. I'm looking more into it. > > -- Steve Thanks, -Beau
