Hello Jens, The blk-mq timeout handling rework that went upstream during the v4.18 development cycle introduced a performance regression due to the atomic instructions that were added in the hot path. This patch series improves blk-mq performance by reducing the number of atomic instructions in the hot path. This patch series increases the number of IOPS reported by a fio test against the null_blk driver with 15% on an x86_64 system. This patch series applies on top of a merge of your for-next and for-linus branches. This patch series passes the block and srp blktests tests. Bart. Changes compared to v1: - Dropped the patch that renames BLK_EH_DONE into BLK_EH_DONT_RESET_TIMER. - Added a new patch that introduces the timeout handler return code BLK_EH_DONT_COMPLETE. - If blk_mq_complete_request() is called from inside the request timed out function, complete the request immediately to avoid triggering a deadlock. - Instead of introducing one new request state, introduce two new request states, namely MQ_RQ_COMPLETION_DELAYED and MQ_RQ_TIMED_OUT. - Fixed a race condition in blk_mq_change_rq_state(). Bart Van Assche (5): blk-mq: Introduce the timeout handler return code BLK_EH_DONT_COMPLETE block: Remove a superfluous #include directive block: Split blk_add_timer() block: Simplify blk_add_timer() and blk_mq_add_timer() blk-mq: Rework blk-mq timeout handling again Documentation/scsi/scsi_eh.txt | 4 +- block/blk-core.c | 3 + block/blk-mq-debugfs.c | 8 +- block/blk-mq.c | 325 +++++++++++++++++----- block/blk-mq.h | 10 +- block/blk-timeout.c | 116 +++++--- block/blk.h | 1 + drivers/block/nbd.c | 2 +- drivers/message/fusion/mptsas.c | 2 +- drivers/s390/block/dasd.c | 6 +- drivers/scsi/gdth.c | 2 +- drivers/scsi/libiscsi.c | 6 +- drivers/scsi/megaraid/megaraid_sas_base.c | 2 +- drivers/scsi/mvumi.c | 2 +- drivers/scsi/qla4xxx/ql4_os.c | 2 +- drivers/scsi/scsi_error.c | 18 +- drivers/scsi/scsi_transport_fc.c | 9 +- drivers/scsi/scsi_transport_srp.c | 4 +- drivers/scsi/ufs/ufshcd.c | 6 +- include/linux/blk-mq.h | 14 - include/linux/blkdev.h | 60 +++- 21 files changed, 417 insertions(+), 185 deletions(-) -- 2.18.0
