From: Dan Williams <dan.j.williams@intel.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Jan Kara <jack@suse.cz>, linux-nvdimm <linux-nvdimm@lists.01.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>, Ross Zwisler <zwisler@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 2/2] mm/dax: Don't enable huge dax mapping by default
Date: Wed, 20 Mar 2019 08:34:20 -0700 [thread overview]
Message-ID: <CAPcyv4iuAPg3HWh5e8-Ud3oCrvp5AoFmjOzf4bbA+VLgR7NLFg@mail.gmail.com> (raw)
In-Reply-To: <878sxa7ys5.fsf@linux.ibm.com>
On Wed, Mar 20, 2019 at 1:09 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>
> Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> writes:
>
> > Dan Williams <dan.j.williams@intel.com> writes:
> >
> >>
> >>> Now what will be page size used for mapping vmemmap?
> >>
> >> That's up to the architecture's vmemmap_populate() implementation.
> >>
> >>> Architectures
> >>> possibly will use PMD_SIZE mapping if supported for vmemmap. Now a
> >>> device-dax with struct page in the device will have pfn reserve area aligned
> >>> to PAGE_SIZE with the above example? We can't map that using
> >>> PMD_SIZE page size?
> >>
> >> IIUC, that's a different alignment. Currently that's handled by
> >> padding the reservation area up to a section (128MB on x86) boundary,
> >> but I'm working on patches to allow sub-section sized ranges to be
> >> mapped.
> >
> > I am missing something w.r.t code. The below code align that using nd_pfn->align
> >
> > if (nd_pfn->mode == PFN_MODE_PMEM) {
> > unsigned long memmap_size;
> >
> > /*
> > * vmemmap_populate_hugepages() allocates the memmap array in
> > * HPAGE_SIZE chunks.
> > */
> > memmap_size = ALIGN(64 * npfns, HPAGE_SIZE);
> > offset = ALIGN(start + SZ_8K + memmap_size + dax_label_reserve,
> > nd_pfn->align) - start;
> > }
> >
> > IIUC that is finding the offset where to put vmemmap start. And that has
> > to be aligned to the page size with which we may end up mapping vmemmap
> > area right?
Right, that's the physical offset of where the vmemmap ends, and the
memory to be mapped begins.
> > Yes we find the npfns by aligning up using PAGES_PER_SECTION. But that
> > is to compute howmany pfns we should map for this pfn dev right?
> >
>
> Also i guess those 4K assumptions there is wrong?
Yes, I think to support non-4K-PAGE_SIZE systems the 'pfn' metadata
needs to be revved and the PAGE_SIZE needs to be recorded in the
info-block.
next prev parent reply other threads:[~2019-03-20 15:34 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
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 [this message]
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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