nvme: optimize passthrough IOPOLL completion for local ring context #491
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added 2 commits
January 22, 2026 19:06
Add a third parameter 'const struct io_comp_batch *' to the rq_end_io_fn callback signature. This allows end_io handlers to access the completion batch context when requests are completed via blk_mq_end_request_batch(). The io_comp_batch is passed from blk_mq_end_request_batch(), while NULL is passed from __blk_mq_end_request() and blk_mq_put_rq_ref() which don't have batch context. This infrastructure change enables drivers to detect whether they're being called from a batched completion path (like iopoll) and access additional context stored in the io_comp_batch. Update all rq_end_io_fn implementations: - block/blk-mq.c: blk_end_sync_rq - block/blk-flush.c: flush_end_io, mq_flush_data_end_io - drivers/nvme/host/ioctl.c: nvme_uring_cmd_end_io - drivers/nvme/host/core.c: nvme_keep_alive_end_io - drivers/nvme/host/pci.c: abort_endio, nvme_del_queue_end, nvme_del_cq_end - drivers/nvme/target/passthru.c: nvmet_passthru_req_done - drivers/scsi/scsi_error.c: eh_lock_door_done - drivers/scsi/sg.c: sg_rq_end_io - drivers/scsi/st.c: st_scsi_execute_end - drivers/target/target_core_pscsi.c: pscsi_req_done - drivers/md/dm-rq.c: end_clone_request Signed-off-by: Ming Lei <ming.lei@redhat.com>
When multiple io_uring rings poll on the same NVMe queue, one ring can find completions belonging to another ring. The current code always uses task_work to handle this, but this adds overhead for the common single-ring case. This patch passes the polling io_ring_ctx through io_comp_batch's new poll_ctx field. In io_do_iopoll(), the polling ring's context is stored in iob.poll_ctx before calling the iopoll callbacks. In nvme_uring_cmd_end_io(), we now compare iob->poll_ctx with the request's owning io_ring_ctx (via io_uring_cmd_ctx_handle()). If they match (local context), we complete inline with io_uring_cmd_done32(). If they differ (remote context) or iob is NULL (non-iopoll path), we use task_work as before. This optimization eliminates task_work scheduling overhead for the common case where a ring polls and finds its own completions. ~10% IOPS improvement is observed in the following benchmark: fio/t/io_uring -b512 -d128 -c32 -s32 -p1 -F1 -O0 -P1 -u1 -n1 /dev/ng0n1 Signed-off-by: Ming Lei <ming.lei@redhat.com>
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Pull request for series with
subject: nvme: optimize passthrough IOPOLL completion for local ring context
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1042707