Linux's user-space block device driver framework "ublk" for implementing virtual block device drivers in user-space relayed by IO_uring is introducing batch I/O dispatch infrastructure.

This code on the way to the mainline kernel for Linux 7.0 allows for delivering I/O commands to the ublk user-space server in batches. By batching the I/O, there is "significantly" reduced notification overhead by allowing multiple I/O completions within a single uring_cmd.

The [1]patch series notes for 16 jobs I/O involving page copies the performance improved in tests by 12% or around 3.7% when using zero-copy. Or for single job I/O was still around a 2.3% improvement with page copies or up to 7% with zero-copy behavior.

"This patchset adds UBLK_F_BATCH_IO feature for communicating between kernel and ublk server in batching way:

- Per-queue vs Per-I/O: Commands operate on queues rather than individual I/Os

- Batch processing: Multiple I/Os are handled in single operation

- Multishot commands: Use io_uring multishot for reducing submission overhead

- Flexible task assignment: Any task can handle any I/O (no per-I/O daemons)

- Better load balancing: Tasks can adjust their workload dynamically

- help for future optimizations:

- blk-mq batch tags free

- support io-poll

- per-task batch for avoiding per-io lock

- fetch command priority

- simplify command cancel process with per-queue lock"

The work is queued up in Jens Axboe's [2]"for-next" Git branch thus on track for the Linux 6.20~7.0 kernel merge window in February barring any unexpected issues.



[1] https://lore.kernel.org/all/20260116141859.719929-1-ming.lei@redhat.com/

[2] https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git/commit/?h=for-next&id=7a1bb41947cee3aa50fa9b276e9aeb6caa87b543