> SCSI's reply qeueue is very similar with blk-mq's hw queue, both
assigned by
> IRQ vector, so map te private reply queue into blk-mq's hw queue via
> .host_tagset.
>
> Then the private reply mapping can be removed.
>
> Another benefit is that the request/irq lost issue may be solved in
generic
> approach because managed IRQ may be shutdown during CPU hotplug.
Ming,
I quickly tested this patch series on MegaRaid Aero controller. Without
this patch I can get 3.0M IOPS, but once I apply this patch I see only
1.2M IOPS (40% Performance drop)
HBA supports 5089 can_queue.
<perf top> output without patch -
3.39% [megaraid_sas] [k] complete_cmd_fusion
3.36% [kernel] [k] scsi_queue_rq
3.26% [kernel] [k] entry_SYSCALL_64
2.57% [kernel] [k] syscall_return_via_sysret
1.95% [megaraid_sas] [k] megasas_build_and_issue_cmd_fusion
1.88% [kernel] [k] _raw_spin_lock_irqsave
1.79% [kernel] [k] gup_pmd_range
1.73% [kernel] [k] _raw_spin_lock
1.68% [kernel] [k] __sched_text_start
1.19% [kernel] [k] irq_entries_start
1.13% [kernel] [k] scsi_dec_host_busy
1.08% [kernel] [k] aio_complete
1.07% [kernel] [k] read_tsc
1.01% [kernel] [k] blk_mq_get_request
0.93% [kernel] [k] __update_load_avg_cfs_rq
0.92% [kernel] [k] aio_read_events
0.91% [kernel] [k] lookup_ioctx
0.91% fio [.] fio_gettime
0.87% [kernel] [k] set_next_entity
0.87% [megaraid_sas] [k] megasas_build_ldio_fusion
<perf top> output with patch -
11.30% [kernel] [k] native_queued_spin_lock_slowpath
3.37% [kernel] [k] sbitmap_any_bit_set
2.91% [kernel] [k] blk_mq_run_hw_queue
2.32% [kernel] [k] _raw_spin_lock_irqsave
2.29% [kernel] [k] menu_select
2.04% [kernel] [k] entry_SYSCALL_64
2.03% [kernel] [k] __sched_text_start
1.70% [kernel] [k] scsi_queue_rq
1.66% [kernel] [k] _raw_spin_lock
1.58% [kernel] [k] syscall_return_via_sysret
1.33% [kernel] [k] native_write_msr
1.20% [kernel] [k] read_tsc
1.13% [kernel] [k] blk_mq_run_hw_queues
1.13% [kernel] [k] __sbq_wake_up
1.01% [kernel] [k] irq_entries_start
1.00% [kernel] [k] switch_mm_irqs_off
0.99% [kernel] [k] gup_pmd_range
0.98% [kernel] [k] __update_load_avg_cfs_rq
0.98% [kernel] [k] set_next_entity
0.92% [kernel] [k] do_idle
Kashyap
