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virtio_balloon: specify page reporting order if needed

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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: Gavin Shan <gshan@redhat.com>
Reviewed-by: Alexander 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Gavin Shan 2021-06-28 19:35:25 -07:00 committed by Linus Torvalds
parent 9f849c6f95
commit f8af4d0892
1 changed files with 17 additions and 0 deletions
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17
drivers/virtio/virtio_balloon.c
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@ -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;