vm_page_startup: correct calculation of the starting page

[kib]

Summary

Also avoid unneded calculations when phys segment end is the phys_avail[] start.

Submitted by: alc
Fixes: 181bfb42fd01bfa9f46

[alc]

sys/vm/vm_page.c

785

Is this still needed?

[kib]

sys/vm/vm_page.c

785

I believe it is in the same state as it was before the fix. I.e. I think the code below would correctly handle a pass while startp == endp, including the vm_phys_enqueue_contig() call. But still, being explicit and tolerate e.g. empty phys_avail[] segments from MD code (for instance MD code doing early allocations and leaving empty segments around) would be not bad.

I can remove this check if you prefer, of course.

[alc]

sys/vm/vm_page.c

785

Then, for this change, I would only suggest moving the m calculation after the continue.

Separately, I think that an empty phys_avail[] segment from the MD code deserves a warning message from the MI code.

794–795

Why is this repeated?

796

[kib]

Move m calculation.
Microoptimize setting of vmd_segs bitmap.