6 Oct
2021
6 Oct
'21
4:24 p.m.
On 06/10/2021 17:08, Michael Kelley wrote:
The calculated value of can_queue is not realistic. The blk-mq layer caps the number of tags at 10240,
nit: 1024, I think
I was thinking about BLK_MQ_MAX_DEPTH (#define'd as 10240), which is used to limit the tag set size in blk_mq_alloc_tag_set(). When running on large VMs on Hyper-V, we can see the "blk-mq: reduced tag depth to 10240" message.:-(
Ah, right. The other related capping is the sdev queue depth, which is now capped at max(1024, can_queue), see scsi_device_max_queue_depth().
Thanks, John