On Mon, Jul 04, 2022 at 05:32:33AM +0100, Russell King (Oracle) wrote: > 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" ? include/asm-generic/getorder.h: * get_order - Determine the allocation order of a memory size > "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!
