On 10/30/20 9:51 AM, Naohiro Aota wrote:
In ZONED, btrfs uses per-FS zoned_meta_io_lock to serialize the metadata write IOs. Even with these serialization, write bios sent from btree_write_cache_pages can be reordered by async checksum workers as these workers are per CPU and not per zone. To preserve write BIO ordering, we can disable async metadata checksum on ZONED. This does not result in lower performance with HDDs as a single CPU core is fast enough to do checksum for a single zone write stream with the maximum possible bandwidth of the device. If multiple zones are being written simultaneously, HDD seek overhead lowers the achievable maximum bandwidth, resulting again in a per zone checksum serialization not affecting performance. Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Thanks, Josef
