[PATCH v3 13/15] virtio-mem: Unplug subblocks right-to-left

David Hildenbrand
2020-05-07T10:33:40Z

We unplug blocks right-to-left, let's also unplug subblocks within a block
right-to-left.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
drivers/virtio/virtio_mem.c | 38 ++++++++++++++++---------------------
1 file changed, 16 insertions(+), 22 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 8dd57b61b09b..a719e1a04ac7 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -353,18 +353,6 @@ static bool virtio_mem_mb_test_sb_unplugged(struct virtio_mem *vm,
return find_next_bit(vm->sb_bitmap, bit + count, bit) >= bit + count;
}

-/*
- * Find the first plugged subblock. Returns vm->nb_sb_per_mb in case there is
- * none.
- */
-static int virtio_mem_mb_first_plugged_sb(struct virtio_mem *vm,
- unsigned long mb_id)
-{
- const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb;
-
- return find_next_bit(vm->sb_bitmap, bit + vm->nb_sb_per_mb, bit) - bit;
-}
-
/*
* Find the first unplugged subblock. Returns vm->nb_sb_per_mb in case there is
* none.
@@ -1016,21 +1004,27 @@ static int virtio_mem_mb_unplug_any_sb(struct virtio_mem *vm,
int sb_id, count;
int rc;

+ sb_id = vm->nb_sb_per_mb - 1;
while (*nb_sb) {
- sb_id = virtio_mem_mb_first_plugged_sb(vm, mb_id);
- if (sb_id >= vm->nb_sb_per_mb)
+ /* Find the next candidate subblock */
+ while (sb_id >= 0 &&
+ virtio_mem_mb_test_sb_unplugged(vm, mb_id, sb_id, 1))
+ sb_id--;
+ if (sb_id < 0)
break;
+ /* Try to unplug multiple subblocks at a time */
count = 1;
- while (count < *nb_sb &&
- sb_id + count < vm->nb_sb_per_mb &&
- virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id + count,
- 1))
+ while (count < *nb_sb && sb_id > 0 &&
+ virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id - 1, 1)) {
count++;
+ sb_id--;
+ }

rc = virtio_mem_mb_unplug_sb(vm, mb_id, sb_id, count);
if (rc)
return rc;
*nb_sb -= count;
+ sb_id--;
}

return 0;
@@ -1337,12 +1331,12 @@ static int virtio_mem_mb_unplug_any_sb_online(struct virtio_mem *vm,
* we should sense via something like is_mem_section_removable()
* first if it makes sense to go ahead any try to allocate.
*/
- for (sb_id = 0; sb_id < vm->nb_sb_per_mb && *nb_sb; sb_id++) {
+ for (sb_id = vm->nb_sb_per_mb - 1; sb_id >= 0 && *nb_sb; sb_id--) {
/* Find the next candidate subblock */
- while (sb_id < vm->nb_sb_per_mb &&
+ while (sb_id >= 0 &&
!virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
- sb_id++;
- if (sb_id >= vm->nb_sb_per_mb)
+ sb_id--;
+ if (sb_id < 0)
break;

start_pfn = PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) +
--
2.25.3