Commit 02872718 authored by Yu Kuai's avatar Yu Kuai
Browse files

scsi_lib: disable fair tag sharing by default if total tags is less than 128 

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8RGGC


CVE: NA

-----------------------------------------------

If total number of driver tags is little, disable the block layer fair tag
sharing algorithm because it significantly reduces performance, e.g.
UFS devices.

Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>
parent 87b42a15

drivers/scsi/scsi_lib.c

+3 −0
Original line number Diff line number Diff line
@@ -1958,6 +1958,7 @@ static const struct blk_mq_ops scsi_mq_ops = { 
	.get_rq_budget_token = scsi_mq_get_rq_budget_token,

};



#define FAIR_TAG_SHARING_THRESHOLD 128

int scsi_mq_setup_tags(struct Scsi_Host *shost)

{

	unsigned int cmd_size, sgl_size;
@@ -1983,6 +1984,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) 
	tag_set->flags = BLK_MQ_F_SHOULD_MERGE;

	tag_set->flags |=

		BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy);

	if (tag_set->queue_depth <= FAIR_TAG_SHARING_THRESHOLD)

		tag_set->flags |= BLK_MQ_F_DISABLE_FAIR_TAG_SHARING;

	if (shost->queuecommand_may_block)

		tag_set->flags |= BLK_MQ_F_BLOCKING;

	tag_set->driver_data = shost;