The patch titled
Subject: device-dax: compound devmap support
has been added to the -mm tree. Its filename is
device-dax-compound-devmap-support.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/device-dax-compound-devmap-support.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/device-dax-compound-devmap-support.patch
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------------------------------------------------------
From: Joao Martins <joao.m.martins@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx/
Link: https://lkml.kernel.org/r/20211202204422.26777-12-joao.m.martins@xxxxxxxxxx
Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Jane Chu <jane.chu@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/dax/device.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/drivers/dax/device.c~device-dax-compound-devmap-support
+++ a/drivers/dax/device.c
@@ -78,14 +78,20 @@ static void dax_set_mapping(struct vm_fa
{
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_da
}
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);
_
Patches currently in -mm which might be from joao.m.martins@xxxxxxxxxx are
mm-page_alloc-split-prep_compound_page-into-head-and-tail-subparts.patch
mm-page_alloc-refactor-memmap_init_zone_device-page-init.patch
mm-memremap-add-zone_device-support-for-compound-pages.patch
device-dax-use-align-for-determining-pgoff.patch
device-dax-use-struct_size.patch
device-dax-ensure-dev_dax-pgmap-is-valid-for-dynamic-devices.patch
device-dax-factor-out-page-mapping-initialization.patch
device-dax-set-mapping-prior-to-vmf_insert_pfn_pmdpud.patch
device-dax-remove-pfn-from-__dev_dax_ptepmdpud_fault.patch
device-dax-compound-devmap-support.patch
