On Sun, Jul 03, 2022 at 10:54:49PM +0100, Matthew Wilcox wrote: > On Sun, Jul 03, 2022 at 10:16:45PM +0100, Russell King (Oracle) wrote: > > On Sun, Jul 03, 2022 at 10:14:41PM +0100, Matthew Wilcox (Oracle) wrote: > > > This is the number of bits used by a PMD entry, not the order of a PMD. > > > > No, it's not the number of bits. A PMD entry doesn't fit in 2 or 3 bits. > > This is even more confusing. > > Well, what is it then? The order of something is PAGE_SIZE << n, and > that doesn't seem to be what this is. Where is it defined that "order" means "PAGE_SIZE << n" ? "order" here is "order of magnitude" and in this case, it is 2^n, just like order of magnitude in base 10 is 10^n. So strictly, the usage here is completely correct, but if you describe "order" as "PAGE_SIZE << n" that is no longer an order of magnitude, because it doesn't increase in an order of magnitude (iow, n = 2 isn't PAGE_SIZE * PAGE_SIZE). Now, if you're trying to tell me that Linux has decided to define "order" to be something non-standard, I'll accept that, but then we shouldn't be renaming stuff that is using it in a standard way. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
