In D21592#473571, @jeff wrote:

In D21592#473568, @markj wrote:

I think I've brought this up before, but I would like it if the VM had a generic per-2MB page structure. We already have several in vm_reserv and the pmap, and IMO it would be a good place to maintain a "compound" busy state, rather than in the object. I worry that a mechanism to block the busying of all pages in an object will inhibit concurrency and lead to transient latency spikes. I don't object to the current approach though.

Right now the object lock is the mechanism that blocks busying of all pages and creates transient latency spikes. This at least narrows it a level and allows other object operations to proceed. If you had a per-superpage object you would have to be able to very quickly look it up and acquire in tryxbusy/sbusy.
Ultimately I would like to see a generic mechanism that can treat pages as groups with a single set of state. A variable page size.

This looks fine to me, but I have no idea why John put PCI_RES_BUS under #ifdef NEW_PCIB instead of defining it always. Also, would it be reasonable to do a separate pass to rename PCI_RES_BUS to SYS_RES_PCIBUS ?

I think it would be fair to remove copyrights from machine/resource.h, instead put the trivial header files into public domain or assign to yourself.

I think it is fine.

In D21667#472964, @mjg wrote:

I think it's cleaner to handle this separately mostly because this function cannot do any clean up so it behaves quite differently compared to vn_start_write. If you insist I can fold it in.

Why do you need vn_start_write_nb() when vn_start_write() already takes the flag argument ?

In D21678#472744, @mjg wrote:

In D21642#472677, @markj wrote:

In D21642#472503, @alc wrote:

Yes, I put the const in the wrong place. So, code within vm_page.c will avoid the dereference, but code outside vm_page.c that uses the declaration from vm_page.h will still perform the dereference. Declaring vm_page_array as an array would deal with both cases.

I'm still missing something. vm_page_array cannot be defined in vm_page.h, and if it is not defined there I do not see how the compiler can elide a memory dereference.

It cannot be defined, but can be declared, same as now. Or I do not understand what you are trying to say.

This is not yet updated to pcpu counters, right ?

Build fixes: tb passes.

Rebase after riscv commit.

I am fine with this version modulo atomic_short.

• Stop overloading KERN_INVALID_ADDRESS for out-of-object error. This breaks other situations, it seems that the best route is to add a new Mach-style error.
• Switch to use switch in signal decoding in vm_fault_trap().
• Do not assume that map == kernel_map implies signo != NULL. copyin faults on user address, but in kernel mode.