From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx204.postini.com [74.125.245.204]) by kanga.kvack.org (Postfix) with SMTP id E71E76B0032 for ; Thu, 6 Jun 2013 23:55:39 -0400 (EDT) Received: from /spool/local by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 7 Jun 2013 13:49:46 +1000 Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [9.190.235.152]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id BB7B42BB0051 for ; Fri, 7 Jun 2013 13:55:30 +1000 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r573erw466191382 for ; Fri, 7 Jun 2013 13:40:54 +1000 Received: from d23av03.au.ibm.com (loopback [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r573tSoq024759 for ; Fri, 7 Jun 2013 13:55:29 +1000 From: "Aneesh Kumar K.V" Subject: Re: [PATCH -V7 09/18] powerpc: Switch 16GB and 16MB explicit hugepages to a different page table format In-Reply-To: <1370558559.32518.4@snotra> References: <1367177859-7893-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1367177859-7893-10-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1370558559.32518.4@snotra> Date: Fri, 07 Jun 2013 09:25:22 +0530 Message-ID: <87zjv2wp5h.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Scott Wood Cc: benh@kernel.crashing.org, paulus@samba.org, dwg@au1.ibm.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org Scott Wood writes: > On 04/28/2013 02:37:30 PM, Aneesh Kumar K.V wrote: >> From: "Aneesh Kumar K.V" >> >> 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 >> --- >> 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org