Use try_grab_compound_head() for device-dax GUP when configured with a
compound pagemap.
Rather than incrementing the refcount for each page, do one atomic
addition for all the pages to be pinned.
Performance measured by gup_benchmark improves considerably
get_user_pages_fast() and pin_user_pages_fast() with NVDIMMs:
$ gup_test -f /dev/dax1.0 -m 16384 -r 10 -S [-u,-a] -n 512 -w
(get_user_pages_fast 2M pages) ~59 ms -> ~6.1 ms
(pin_user_pages_fast 2M pages) ~87 ms -> ~6.2 ms
[altmap]
(get_user_pages_fast 2M pages) ~494 ms -> ~9 ms
(pin_user_pages_fast 2M pages) ~494 ms -> ~10 ms
$ gup_test -f /dev/dax1.0 -m 129022 -r 10 -S [-u,-a] -n 512 -w
(get_user_pages_fast 2M pages) ~492 ms -> ~49 ms
(pin_user_pages_fast 2M pages) ~493 ms -> ~50 ms
[altmap with -m 127004]
(get_user_pages_fast 2M pages) ~3.91 sec -> ~70 ms
(pin_user_pages_fast 2M pages) ~3.97 sec -> ~74 ms
Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
---
mm/gup.c | 53 +++++++++++++++++++++++++++++++++--------------------
1 file changed, 33 insertions(+), 20 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 42b8b1fa6521..9baaa1c0b7f3 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2234,31 +2234,55 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
}
#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
+
+static int record_subpages(struct page *page, unsigned long addr,
+ unsigned long end, struct page **pages)
+{
+ int nr;
+
+ for (nr = 0; addr != end; addr += PAGE_SIZE)
+ pages[nr++] = page++;
+
+ return nr;
+}
+
#if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
static int __gup_device_huge(unsigned long pfn, unsigned long addr,
unsigned long end, unsigned int flags,
struct page **pages, int *nr)
{
- int nr_start = *nr;
+ int refs, nr_start = *nr;
struct dev_pagemap *pgmap = NULL;
do {
- struct page *page = pfn_to_page(pfn);
+ struct page *pinned_head, *head, *page = pfn_to_page(pfn);
+ unsigned long next;
pgmap = get_dev_pagemap(pfn, pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, flags, pages);
return 0;
}
- SetPageReferenced(page);
- pages[*nr] = page;
- if (unlikely(!try_grab_page(page, flags))) {
- undo_dev_pagemap(nr, nr_start, flags, pages);
+
+ head = compound_head(page);
+ /* @end is assumed to be limited at most one compound page */
+ next = PageCompound(head) ? end : addr + PAGE_SIZE;
+ refs = record_subpages(page, addr, next, pages + *nr);
+
+ SetPageReferenced(head);
+ pinned_head = try_grab_compound_head(head, refs, flags);
+ if (!pinned_head) {
+ if (PageCompound(head)) {
+ ClearPageReferenced(head);
+ put_dev_pagemap(pgmap);
+ } else {
+ undo_dev_pagemap(nr, nr_start, flags, pages);
+ }
return 0;
}
- (*nr)++;
- pfn++;
- } while (addr += PAGE_SIZE, addr != end);
+ *nr += refs;
+ pfn += refs;
+ } while (addr += (refs << PAGE_SHIFT), addr != end);
if (pgmap)
put_dev_pagemap(pgmap);
@@ -2318,17 +2342,6 @@ static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
}
#endif
-static int record_subpages(struct page *page, unsigned long addr,
- unsigned long end, struct page **pages)
-{
- int nr;
-
- for (nr = 0; addr != end; addr += PAGE_SIZE)
- pages[nr++] = page++;
-
- return nr;
-}
-
#ifdef CONFIG_ARCH_HAS_HUGEPD
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
unsigned long sz)
--
2.17.1
