Subject: Re: uvm_km_valloc_align() and USPACE (Re: CVS commit: syssrc)
To: None <email@example.com, firstname.lastname@example.org>
From: Chris Torek <torek@BSDI.COM>
Date: 12/02/2000 22:47:30
>Umm.. NBPG was constant but PAGE_SIZE was not?
>Or NBPG was a hardware value and PAGE_SIZE was for vm?
The latter. This was all clearer in the 4.BSD system before
the Mach VM went in:
NBPG: hardware page size in bytes
CLSIZE: "cluster" size for making bigger VM pages out of
small hardware pages
I forget whether PGOFSET was NBPG-1 or CLBYTES-1, though. CLSIZE
was 2 (on the VAX) so that the OS could pretend the hardware had
1024-byte pages, and reduce the paging overhead.
On the Tahoe, 68020, and other "post-4.3BSD" non-VAX ports, CLSIZE
was effectively always 1.