Commit f8af4d08 authored by Gavin Shan's avatar Gavin Shan Committed by Linus Torvalds
Browse files

virtio_balloon: specify page reporting order if needed 

The page reporting won't be triggered if the freeing page can't come up
with a free area, whose size is equal or bigger than the threshold (page
reporting order).  The default page reporting order, equal to
@pageblock_order, is too huge on some architectures to trigger page
reporting.  One example is ARM64 when 64KB base page size is used.

      PAGE_SIZE:          64KB
      pageblock_order:    13       (512MB)
      MAX_ORDER:          14

This specifies the page reporting order to 5 (2MB) for this specific case
so that page reporting can be triggered.

Link: https://lkml.kernel.org/r/20210625014710.42954-5-gshan@redhat.com


Signed-off-by: default avatarGavin Shan <gshan@redhat.com>
Reviewed-by: default avatarAlexander Duyck <alexanderduyck@fb.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9f849c6f

drivers/virtio/virtio_balloon.c

+17 −0
Original line number Diff line number Diff line
@@ -993,6 +993,23 @@ static int virtballoon_probe(struct virtio_device *vdev) 
			goto out_unregister_oom;

		}



		/*

		 * The default page reporting order is @pageblock_order, which

		 * corresponds to 512MB in size on ARM64 when 64KB base page

		 * size is used. The page reporting won't be triggered if the

		 * freeing page can't come up with a free area like that huge.

		 * So we specify the page reporting order to 5, corresponding

		 * to 2MB. It helps to avoid THP splitting if 4KB base page

		 * size is used by host.

		 *

		 * Ideally, the page reporting order is selected based on the

		 * host's base page size. However, it needs more work to report

		 * that value. The hard-coded order would be fine currently.

		 */

#if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES)

		vb->pr_dev_info.order = 5;

#endif



		err = page_reporting_register(&vb->pr_dev_info);

		if (err)

			goto out_unregister_oom;