Commit 14606001 authored by Joao Martins's avatar Joao Martins Committed by Linus Torvalds

device-dax: compound devmap support

Use the newly added compound devmap facility which maps the assigned dax
ranges as compound pages at a page size of @align.

dax devices are created with a fixed @align (huge page size) which is
enforced through as well at mmap() of the device.  Faults, consequently
happen too at the specified @align specified at the creation, and those
don't change throughout dax device lifetime.  MCEs unmap a whole dax
huge page, as well as splits occurring at the configured page size.

Performance measured by gup_test improves considerably for
unpin_user_pages() and altmap with NVDIMMs:

  $ gup_test -f /dev/dax1.0 -m 16384 -r 10 -S -a -n 512 -w
  (pin_user_pages_fast 2M pages) put:~71 ms -> put:~22 ms
  [altmap]
  (pin_user_pages_fast 2M pages) get:~524ms put:~525 ms -> get: ~127ms put:~71ms

   $ gup_test -f /dev/dax1.0 -m 129022 -r 10 -S -a -n 512 -w
  (pin_user_pages_fast 2M pages) put:~513 ms -> put:~188 ms
  [altmap with -m 127004]
  (pin_user_pages_fast 2M pages) get:~4.1 secs put:~4.12 secs -> get:~1sec put:~563ms

.. as well as unpin_user_page_range_dirty_lock() being just as effective
as THP/hugetlb[0] pages.

[0] https://lore.kernel.org/linux-mm/20210212130843.13865-5-joao.m.martins@oracle.com/

Link: https://lkml.kernel.org/r/20211202204422.26777-12-joao.m.martins@oracle.comSigned-off-by: default avatarJoao Martins <joao.m.martins@oracle.com>
Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6ec228b6
......@@ -78,14 +78,20 @@ static void dax_set_mapping(struct vm_fault *vmf, pfn_t pfn,
{
unsigned long i, nr_pages = fault_size / PAGE_SIZE;
struct file *filp = vmf->vma->vm_file;
struct dev_dax *dev_dax = filp->private_data;
pgoff_t pgoff;
/* mapping is only set on the head */
if (dev_dax->pgmap->vmemmap_shift)
nr_pages = 1;
pgoff = linear_page_index(vmf->vma,
ALIGN(vmf->address, fault_size));
for (i = 0; i < nr_pages; i++) {
struct page *page = pfn_to_page(pfn_t_to_pfn(pfn) + i);
page = compound_head(page);
if (page->mapping)
continue;
......@@ -443,6 +449,9 @@ int dev_dax_probe(struct dev_dax *dev_dax)
}
pgmap->type = MEMORY_DEVICE_GENERIC;
if (dev_dax->align > PAGE_SIZE)
pgmap->vmemmap_shift =
order_base_2(dev_dax->align >> PAGE_SHIFT);
addr = devm_memremap_pages(dev, pgmap);
if (IS_ERR(addr))
return PTR_ERR(addr);
......
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