On Wed, May 29, 2024 at 10:14:15AM +0000, Christophe Leroy wrote: > > > Le 29/05/2024 à 12:09, Oscar Salvador a écrit : > > On Wed, May 29, 2024 at 09:49:48AM +0000, Christophe Leroy wrote: > >> Doesn't really matter if it's PUD or PMD at this point. On a 32 bits > >> kernel it will be all PMD while on a 64 bits kernel it is both PMD and PUD. > >> > >> At the time being (as implemented with hugepd), Linux support 4M, 16M, > >> 64M, 256M and 1G (Shifts 22, 24, 26, 28, 30) > >> > >> The hardware supports the following page sizes, and encodes them on 4 > >> bits allthough it is not directly a shift. Maybe it would be better to > >> use that encoding after all: > > > > I think so. > > > >> > >> 0001 4 Kbytes (Shift 12) > >> 0010 16 Kbytes (Shift 14) > >> 0011 64 Kbytes (Shift 16) > >> 0100 256 Kbytes (Shift 18) > >> 0101 1 Mbyte (Shift 20) > >> 0110 4 Mbytes (Shift 22) > >> 0111 16 Mbytes (Shift 24) > >> 1000 64 Mbytes (Shift 26) > >> 1001 256 Mbytes (Shift 28) > >> 1010 1 Gbyte (e500v2 only) (Shift 30) > >> 1011 4 Gbytes (e500v2 only) (Shift 32) > > > > You say hugehages start at 2MB (shift 21), but you say that the smallest hugepage > > Linux support is 4MB (shift 22).? > > > > > > No I say PMD_SIZE is 2MB on e500 with 64 bits PTE and at the time being > Linux powerpc implementation for e500 supports sizes 4M, 16M, 64M, 256M > and 1G. Got it. I got confused. -- Oscar Salvador SUSE Labs
