Scott Wood <scottwood@xxxxxxxxxxxxx> writes: > On 04/28/2013 02:37:30 PM, Aneesh Kumar K.V wrote: >> From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> >> >> We will be switching PMD_SHIFT to 24 bits to facilitate THP >> impmenetation. >> With PMD_SHIFT set to 24, we now have 16MB huge pages allocated at >> PGD level. >> That means with 32 bit process we cannot allocate normal pages at >> all, because we cover the entire address space with one pgd entry. >> Fix this >> by switching to a new page table format for hugepages. With the new >> page table >> format for 16GB and 16MB hugepages we won't allocate hugepage >> directory. Instead >> we encode the PTE information directly at the directory level. This >> forces 16MB >> hugepage at PMD level. This will also make the page take walk much >> simpler later >> when we add the THP support. >> >> With the new table format we have 4 cases for pgds and pmds: >> (1) invalid (all zeroes) >> (2) pointer to next table, as normal; bottom 6 bits == 0 >> (3) leaf pte for huge page, bottom two bits != 00 >> (4) hugepd pointer, bottom two bits == 00, next 4 bits indicate size >> of table >> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> >> --- >> arch/powerpc/include/asm/page.h | 2 + >> arch/powerpc/include/asm/pgtable.h | 2 + >> arch/powerpc/mm/gup.c | 18 +++- >> arch/powerpc/mm/hugetlbpage.c | 176 >> +++++++++++++++++++++++++++++++------ >> 4 files changed, 168 insertions(+), 30 deletions(-) > > After this patch, on 64-bit book3e (e5500, and thus 4K pages), I see > messages like this after exiting a program that uses hugepages > (specifically, qemu): > > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221516. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221516. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc2214d6. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc2214d6. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221916. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221916. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc2218d6. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc2218d6. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221496. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221496. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221856. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221856. > /home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd > 40000001fc221816. hmm that implies some of the code paths are not properly #ifdef. The goal was to limit the new format CONFIG_PPC_BOOK3S_64 as seen in the definition of huge_pte_alloc. Can you send me the .config ? -aneesh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>