On 11/16/20 10:07 AM, Ming Lei wrote:
SCSI uses one global atomic variable to track queue depth for each LUN/request queue. This way doesn't scale well when there is lots of CPU cores and the disk is very fast. It has been observed that IOPS is affected a lot by tracking queue depth via sdev->device_busy in IO path. Return budget token from .get_budget callback, and the budget token can be passed to driver, so that we can replace the atomic variable with sbitmap_queue, then the scale issue can be fixed. Cc: Omar Sandoval <osandov@xxxxxx> Cc: Kashyap Desai <kashyap.desai@xxxxxxxxxxxx> Cc: Sumanesh Samanta <sumanesh.samanta@xxxxxxxxxxxx> Cc: Ewan D. Milne <emilne@xxxxxxxxxx> Cc: Hannes Reinecke <hare@xxxxxxx> Tested-by: Sumanesh Samanta <sumanesh.samanta@xxxxxxxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- block/blk-mq-sched.c | 17 +++++++++++++---- block/blk-mq.c | 36 +++++++++++++++++++++++++----------- block/blk-mq.h | 25 +++++++++++++++++++++---- drivers/scsi/scsi_lib.c | 16 +++++++++++----- include/linux/blk-mq.h | 4 ++-- 5 files changed, 72 insertions(+), 26 deletions(-) Reviewed-by: Hannes Reinecke <hare@xxxxxxx
Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@xxxxxxx +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
