[PATCH 0/2] btrfs: zoned: fix bandwidth degradaton

[Naohiro Aota <Naohiro.Aota@wdc.com>]

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Writing sequentially to a huge file on btrfs on a SMR HDD revealed a
decline of the performance (220 MiB/s to 30 MiB/s after 500 minutes). As
shown in the attached plot, current btrfs exponentially drops its
performance.

The drop is because find_free_extent() need to traverse a lot of full block
groups, trying to find a space.

This series fixes the performance drop by choosing a proper block group
from the zone_active_bgs. Since the list does not contain full block
groups, there is no need of traversing the full BGs. 

Naohiro Aota (2):
  btrfs: zoned: split out prepare_allocation_zoned()
  btrfs: zoned: optimize hint byte for zoned allocator

 fs/btrfs/extent-tree.c | 50 +++++++++++++++++++++++++++++++-----------
 1 file changed, 37 insertions(+), 13 deletions(-)

-- 
2.43.0


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