Similarly, there is no reason to define VM_KMEM_SIZE_MIN.

In D27956#627791, @kib wrote:

In D27956#627736, @markj wrote:

Do riscv or arm64 have the same bug?

No, this bug was introduced with LA57 rewrite of pmap_allocpte(). riscv and arm64 forked pmap.c before LA57.

That's all that I have.

I have nothing more to add. Once you've dealt with Mark's latest comment, commit it. I don't see the need for me to look at this change again.

I'd be interested in seeing the output of sysctl vm.phys_segs on one of these machines. Can you post it here?

I ran into a similar problem with respect to vm_phys_segs[] in eliminating iteration from the vm_dumpset operations. I wonder if we shouldn't separate the struct vm_phys_seg and array declarations into their own separate header file that is included by vm_param.h. Then, vm_page.h could implement vm_page_domain().

Here is my first batch of comments.

After mulling this over for the past day or so, I'd like to propose the following alternative description:

I'm afraid that I can't make sense out of the summary. Is this a problem with the KASSERT that precedes the pmap lock acquire in arm64's pmap_remove_pages()? Omce pmap_remove_pages() has performed the lock acquire, prior changes to the pmap should be visible to it.

In D26876#599253, @markj wrote:

Most other implementations also use bzero(), though on them pagezero() is nothing more than bzero(va, PAGE_SIZE) anyway.

A while back, Intel quietly made it possible to measure address translation overhead for instruction accesses. I say, "quietly," because the manual provides a low-level description of the counter that doesn't really explain what it effectively measures. However, some Intel people gave a presentation at an HPC workshop about 2 years ago that explained the counter's meaning, and Intel published those slides here: https://software.intel.com/content/www/us/en/develop/download/how-top-down-microarchitecture-analysis-tma-addresses-challenges-in-modern-servers.html

By the way, in case you are going to use the summary in the commit message, "reclamining" is misspelled.

Alternatively, move this code to a different header file. None of the new dump-related code uses struct vm_page.

Is it documented anywhere what can versus can't be done to a non-transparent mapping?

I'd suggest that you add a comment explaining why the assertion has to be written this way.