Both hugetlb and thp locate on the same migration type of pageblock, since
they are allocated from a free_list[]. Based on this fact, it is enough to
check on a single subpage to decide the migration type of the whole huge
page. By this way, it saves (2M/4K - 1) times loop for pmd_huge on x86,
similar on other archs.
Furthermore, when executing isolate_huge_page(), it avoid taking global
hugetlb_lock many times, and meanless remove/add to the local link list
cma_page_list.
Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Linux-kernel@xxxxxxxxxxxxxxx
---
v3 -> v4: fix C language precedence issue
v4 -> v5: drop the check PageCompound() and improve notes
mm/gup.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index ddde097..1deaad2 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1336,25 +1336,30 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
struct vm_area_struct **vmas,
unsigned int gup_flags)
{
- long i;
+ long i, step;
bool drain_allow = true;
bool migrate_allow = true;
LIST_HEAD(cma_page_list);
check_again:
- for (i = 0; i < nr_pages; i++) {
+ for (i = 0; i < nr_pages;) {
+
+ struct page *head = compound_head(pages[i]);
+
+ /*
+ * gup may start from a tail page. Advance step by the left
+ * part.
+ */
+ step = (1 << compound_order(head)) - (pages[i] - head);
/*
* If we get a page from the CMA zone, since we are going to
* be pinning these entries, we might as well move them out
* of the CMA zone if possible.
*/
- if (is_migrate_cma_page(pages[i])) {
-
- struct page *head = compound_head(pages[i]);
-
- if (PageHuge(head)) {
+ if (is_migrate_cma_page(head)) {
+ if (PageHuge(head))
isolate_huge_page(head, &cma_page_list);
- } else {
+ else {
if (!PageLRU(head) && drain_allow) {
lru_add_drain_all();
drain_allow = false;
@@ -1369,6 +1374,8 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,
}
}
}
+
+ i += step;
}
if (!list_empty(&cma_page_list)) {
--
2.7.5
