| Message ID | 3434830b6fadf644c5a47eaaea6759c375b39ad7.1604065695.git.naohiro.aota@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: zoned block device support | expand |
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@wdc.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Thanks, Josef
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index f02b121d8213..2b30ef8a7034 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -813,6 +813,8 @@ static blk_status_t btree_submit_bio_start(void *private_data, struct bio *bio, static int check_async_write(struct btrfs_fs_info *fs_info, struct btrfs_inode *bi) { + if (btrfs_is_zoned(fs_info)) + return 0; if (atomic_read(&bi->sync_writers)) return 0; if (test_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags))
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@wdc.com> --- fs/btrfs/disk-io.c | 2 ++ 1 file changed, 2 insertions(+)