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From: Scott Wood <scottwood@freescale.com>
To: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: dwg@au1.ibm.com, linux-mm@kvack.org, paulus@samba.org,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH -V7 09/18] powerpc: Switch 16GB and 16MB explicit hugepages to a different page table format
Date: Thu, 6 Jun 2013 17:42:39 -0500	[thread overview]
Message-ID: <1370558559.32518.4@snotra> (raw)
In-Reply-To: <1367177859-7893-10-git-send-email-aneesh.kumar@linux.vnet.ibm.com> (from aneesh.kumar@linux.vnet.ibm.com on Sun Apr 28 14:37:30 2013)

On 04/28/2013 02:37:30 PM, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
>=20
> We will be switching PMD_SHIFT to 24 bits to facilitate THP =20
> impmenetation.
> With PMD_SHIFT set to 24, we now have 16MB huge pages allocated at =20
> 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. =20
> Fix this
> by switching to a new page table format for hugepages. With the new =20
> page table
> format for 16GB and 16MB hugepages we won't allocate hugepage =20
> directory. Instead
> we encode the PTE information directly at the directory level. This =20
> forces 16MB
> hugepage at PMD level. This will also make the page take walk much =20
> simpler later
> when we add the THP support.
>=20
> 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 =3D=3D 0
> (3) leaf pte for huge page, bottom two bits !=3D 00
> (4) hugepd pointer, bottom two bits =3D=3D 00, next 4 bits indicate size =
=20
> of table
>=20
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
>  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 =20
> +++++++++++++++++++++++++++++++------
>  4 files changed, 168 insertions(+), 30 deletions(-)

After this patch, on 64-bit book3e (e5500, and thus 4K pages), I see =20
messages like this after exiting a program that uses hugepages =20
(specifically, qemu):

/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221516.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221516.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc2214d6.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc2214d6.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221916.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221916.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc2218d6.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc2218d6.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221496.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221496.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221856.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221856.
/home/scott/fsl/git/linux/upstream/mm/memory.c:407: bad pmd =20
40000001fc221816.

-Scott=

  parent reply	other threads:[~2013-06-06 22:42 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-28 19:37 [PATCH -V7 00/18] THP support for PPC64 (Patchset 1) Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 01/18] mm/THP: HPAGE_SHIFT is not a #define on some arch Aneesh Kumar K.V
2013-04-30  2:21   ` David Gibson
2013-04-30  2:24     ` David Gibson
2013-04-30  3:42     ` Aneesh Kumar K.V
2013-04-30  5:01       ` David Gibson
2013-05-03 18:51         ` Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 02/18] mm/THP: Add pmd args to pgtable deposit and withdraw APIs Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 03/18] mm/THP: withdraw the pgtable after pmdp related operations Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 04/18] powerpc: Use signed formatting when printing error Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 05/18] powerpc: Save DAR and DSISR in pt_regs on MCE Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 06/18] powerpc: Don't hard code the size of pte page Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 07/18] powerpc: Don't truncate pgd_index wrongly Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 08/18] powerpc: New hugepage directory format Aneesh Kumar K.V
2013-04-30  5:16   ` David Gibson
2013-04-28 19:37 ` [PATCH -V7 09/18] powerpc: Switch 16GB and 16MB explicit hugepages to a different page table format Aneesh Kumar K.V
2013-04-30  5:17   ` David Gibson
2013-06-06 22:42   ` Scott Wood [this message]
2013-06-07  3:55     ` Aneesh Kumar K.V
2013-06-07 19:17       ` Scott Wood
2013-06-08 16:57         ` Aneesh Kumar K.V
2013-06-11 20:53           ` Scott Wood
2013-06-11 22:50             ` Scott Wood
2013-06-12  6:30               ` Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 10/18] powerpc: Reduce the PTE_INDEX_SIZE Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 11/18] powerpc: Move the pte free routines from common header Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 12/18] powerpc: Reduce PTE table memory wastage Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 13/18] powerpc: Use encode avpn where we need only avpn values Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 14/18] powerpc: Decode the pte-lp-encoding bits correctly Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 15/18] powerpc: Fix hpte_decode to use the correct decoding for page sizes Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 16/18] powerpc: print both base and actual page size on hash failure Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 17/18] powerpc: Print page size info during boot Aneesh Kumar K.V
2013-04-28 19:37 ` [PATCH -V7 18/18] powerpc: Update tlbie/tlbiel as per ISA doc Aneesh Kumar K.V
2013-04-30  6:15   ` David Gibson
2013-04-30 17:21     ` Aneesh Kumar K.V
2013-05-01  5:26       ` David Gibson
2013-05-01  7:47         ` Aneesh Kumar K.V
2013-05-01  7:52           ` Simon Jeons
2013-05-01 11:36             ` David Gibson
2013-05-02  5:23           ` David Gibson

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