Hi Jens, The fair tag sharing algorithm reduces performance for UFS devices significantly. This is because UFS devices have multiple logical units, a limited queue depth (32 for UFS 3.1 devices), because it happens often that multiple logical units are accessed and also because it takes time to give tags back after activity on a request queue has stopped. This patch series restores UFS device performance to that of the legacy block layer by disabling fair tag sharing for UFS devices. Please consider this patch series for the next merge window. Thanks, Bart. Changes compared to v5: - Request queues are frozen before fair tag sharing is changed. - Added a sysfs attribute to SCSI hosts for configuring fair tag sharing. Changes compared to v4: - Rebased on top of kernel v6.7-rc1. Changes compared to v3: - Instead of disabling fair tag sharing for all block drivers, introduce a flag for disabling it conditionally. Changes between v2 and v3: - Rebased on top of the latest kernel. Changes between v1 and v2: - Restored the tags->active_queues variable and thereby fixed the "uninitialized variable" warning reported by the kernel test robot. Bart Van Assche (4): block: Make fair tag sharing configurable scsi: core: Make fair tag sharing configurable in the host template scsi: core: Make fair tag sharing configurable via sysfs scsi: ufs: Disable fair tag sharing block/blk-mq-debugfs.c | 1 + block/blk-mq.c | 28 ++++++++++++++++++++++++++++ block/blk-mq.h | 3 ++- drivers/scsi/hosts.c | 1 + drivers/scsi/scsi_lib.c | 2 ++ drivers/scsi/scsi_sysfs.c | 30 ++++++++++++++++++++++++++++++ drivers/ufs/core/ufshcd.c | 1 + include/linux/blk-mq.h | 6 ++++-- include/scsi/scsi_host.h | 6 ++++++ 9 files changed, 75 insertions(+), 3 deletions(-)
