From: Jan Kara <jack@suse.cz>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: akpm@linux-foundation.org,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Jan Kara <jack@suse.cz>,
mpe@ellerman.id.au, Ross Zwisler <zwisler@kernel.org>,
Oliver O'Halloran <oohall@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH 2/2] mm/dax: Don't enable huge dax mapping by default
Date: Thu, 28 Feb 2019 10:40:11 +0100 [thread overview]
Message-ID: <20190228094011.GB22210@quack2.suse.cz> (raw)
In-Reply-To: <20190228083522.8189-2-aneesh.kumar@linux.ibm.com>
On Thu 28-02-19 14:05:22, Aneesh Kumar K.V wrote:
> Add a flag to indicate the ability to do huge page dax mapping. On architecture
> like ppc64, the hypervisor can disable huge page support in the guest. In
> such a case, we should not enable huge page dax mapping. This patch adds
> a flag which the architecture code will update to indicate huge page
> dax mapping support.
>
> Architectures mostly do transparent_hugepage_flag = 0; if they can't
> do hugepages. That also takes care of disabling dax hugepage mapping
> with this change.
>
> Without this patch we get the below error with kvm on ppc64.
>
> [ 118.849975] lpar: Failed hash pte insert with error -4
>
> NOTE: The patch also use
>
> echo never > /sys/kernel/mm/transparent_hugepage/enabled
> to disable dax huge page mapping.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Added Dan to CC for opinion. I kind of fail to see why you don't use
TRANSPARENT_HUGEPAGE_FLAG for this. I know that technically DAX huge pages
and normal THPs are different things but so far we've tried to avoid making
that distinction visible to userspace.
Honza
> ---
> TODO:
> * Add Fixes: tag
>
> include/linux/huge_mm.h | 4 +++-
> mm/huge_memory.c | 4 ++++
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 381e872bfde0..01ad5258545e 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -53,6 +53,7 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
> pud_t *pud, pfn_t pfn, bool write);
> enum transparent_hugepage_flag {
> TRANSPARENT_HUGEPAGE_FLAG,
> + TRANSPARENT_HUGEPAGE_DAX_FLAG,
> TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
> TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
> @@ -111,7 +112,8 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
> if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG))
> return true;
>
> - if (vma_is_dax(vma))
> + if (vma_is_dax(vma) &&
> + (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_DAX_FLAG)))
> return true;
>
> if (transparent_hugepage_flags &
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index faf357eaf0ce..43d742fe0341 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -53,6 +53,7 @@ unsigned long transparent_hugepage_flags __read_mostly =
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
> (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
> #endif
> + (1 << TRANSPARENT_HUGEPAGE_DAX_FLAG) |
> (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
> (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
> (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
> @@ -475,6 +476,8 @@ static int __init setup_transparent_hugepage(char *str)
> &transparent_hugepage_flags);
> clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> &transparent_hugepage_flags);
> + clear_bit(TRANSPARENT_HUGEPAGE_DAX_FLAG,
> + &transparent_hugepage_flags);
> ret = 1;
> }
> out:
> @@ -753,6 +756,7 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
> spinlock_t *ptl;
>
> ptl = pmd_lock(mm, pmd);
> + /* should we check for none here again? */
> entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
> if (pfn_t_devmap(pfn))
> entry = pmd_mkdevmap(entry);
> --
> 2.20.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2019-02-28 9:40 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-28 8:35 [PATCH 1/2] fs/dax: deposit pagetable even when installing zero page Aneesh Kumar K.V
2019-02-28 8:35 ` [PATCH 2/2] mm/dax: Don't enable huge dax mapping by default Aneesh Kumar K.V
2019-02-28 9:40 ` Jan Kara [this message]
2019-02-28 12:32 ` Aneesh Kumar K.V
2019-02-28 9:40 ` Oliver
2019-02-28 12:43 ` Aneesh Kumar K.V
2019-02-28 16:45 ` Dan Williams
2019-03-06 9:17 ` Aneesh Kumar K.V
2019-03-06 11:44 ` Michal Suchánek
2019-03-06 12:45 ` Aneesh Kumar K.V
2019-03-06 13:06 ` Kirill A. Shutemov
2019-03-13 16:07 ` Dan Williams
2019-03-19 8:44 ` Kirill A. Shutemov
2019-03-19 15:36 ` Dan Williams
2019-03-13 16:02 ` Dan Williams
2019-03-14 3:45 ` Aneesh Kumar K.V
2019-03-14 4:02 ` Dan Williams
2019-03-20 8:06 ` Aneesh Kumar K.V
2019-03-20 8:09 ` Aneesh Kumar K.V
2019-03-20 15:34 ` Dan Williams
2019-03-20 20:57 ` Dan Williams
2019-03-21 3:08 ` Oliver
2019-03-21 3:12 ` Dan Williams
2019-02-28 9:21 ` [PATCH 1/2] fs/dax: deposit pagetable even when installing zero page Jan Kara
2019-02-28 12:34 ` Aneesh Kumar K.V
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