RE: [PATCH 0/5] blk-mq/scsi-mq: support global tags & introduce force_blk_mq

Kashyap Desai
2018-02-07T14:14:04Z

> -----Original Message-----
> From: Ming Lei [mailto:ming.lei@redhat.com]
> Sent: Wednesday, February 7, 2018 5:53 PM
> To: Hannes Reinecke
> Cc: Kashyap Desai; Jens Axboe; linux-block@vger.kernel.org; Christoph
> Hellwig; Mike Snitzer; linux-scsi@vger.kernel.org; Arun Easi; Omar
Sandoval;
> Martin K . Petersen; James Bottomley; Christoph Hellwig; Don Brace;
Peter
> Rivera; Paolo Bonzini; Laurence Oberman
> Subject: Re: [PATCH 0/5] blk-mq/scsi-mq: support global tags & introduce
> force_blk_mq
>
> On Wed, Feb 07, 2018 at 07:50:21AM +0100, Hannes Reinecke wrote:
> > Hi all,
> >
> > [ .. ]
> > >>
> > >> Could you share us your patch for enabling global_tags/MQ on
> > > megaraid_sas
> > >> so that I can reproduce your test?
> > >>
> > >>> See below perf top data. "bt_iter" is consuming 4 times more CPU.
> > >>
> > >> Could you share us what the IOPS/CPU utilization effect is after
> > > applying the
> > >> patch V2? And your test script?
> > > Regarding CPU utilization, I need to test one more time. Currently
> > > system is in used.
> > >
> > > I run below fio test on total 24 SSDs expander attached.
> > >
> > > numactl -N 1 fio jbod.fio --rw=randread --iodepth=64 --bs=4k
> > > --ioengine=libaio --rw=randread
> > >
> > > Performance dropped from 1.6 M IOPs to 770K IOPs.
> > >
> > This is basically what we've seen with earlier iterations.
>
> Hi Hannes,
>
> As I mentioned in another mail[1], Kashyap's patch has a big issue,
which
> causes only reply queue 0 used.
>
> [1] https://marc.info/?l=linux-scsi&m=151793204014631&w=2
>
> So could you guys run your performance test again after fixing the
patch?

Ming -

I tried after change you requested. Performance drop is still unresolved.
>From 1.6 M IOPS to 770K IOPS.

See below data. All 24 reply queue is in used correctly.

IRQs / 1 second(s)
IRQ# TOTAL NODE0 NODE1 NAME
360 16422 0 16422 IR-PCI-MSI 70254653-edge megasas
364 15980 0 15980 IR-PCI-MSI 70254657-edge megasas
362 15979 0 15979 IR-PCI-MSI 70254655-edge megasas
345 15696 0 15696 IR-PCI-MSI 70254638-edge megasas
341 15659 0 15659 IR-PCI-MSI 70254634-edge megasas
369 15656 0 15656 IR-PCI-MSI 70254662-edge megasas
359 15650 0 15650 IR-PCI-MSI 70254652-edge megasas
358 15596 0 15596 IR-PCI-MSI 70254651-edge megasas
350 15574 0 15574 IR-PCI-MSI 70254643-edge megasas
342 15532 0 15532 IR-PCI-MSI 70254635-edge megasas
344 15527 0 15527 IR-PCI-MSI 70254637-edge megasas
346 15485 0 15485 IR-PCI-MSI 70254639-edge megasas
361 15482 0 15482 IR-PCI-MSI 70254654-edge megasas
348 15467 0 15467 IR-PCI-MSI 70254641-edge megasas
368 15463 0 15463 IR-PCI-MSI 70254661-edge megasas
354 15420 0 15420 IR-PCI-MSI 70254647-edge megasas
351 15378 0 15378 IR-PCI-MSI 70254644-edge megasas
352 15377 0 15377 IR-PCI-MSI 70254645-edge megasas
356 15348 0 15348 IR-PCI-MSI 70254649-edge megasas
337 15344 0 15344 IR-PCI-MSI 70254630-edge megasas
343 15320 0 15320 IR-PCI-MSI 70254636-edge megasas
355 15266 0 15266 IR-PCI-MSI 70254648-edge megasas
335 15247 0 15247 IR-PCI-MSI 70254628-edge megasas
363 15233 0 15233 IR-PCI-MSI 70254656-edge megasas

Average: CPU %usr %nice %sys %iowait %steal
%irq %soft %guest %gnice %idle
Average: 18 3.80 0.00 14.78 10.08 0.00
0.00 4.01 0.00 0.00 67.33
Average: 19 3.26 0.00 15.35 10.62 0.00
0.00 4.03 0.00 0.00 66.74
Average: 20 3.42 0.00 14.57 10.67 0.00
0.00 3.84 0.00 0.00 67.50
Average: 21 3.19 0.00 15.60 10.75 0.00
0.00 4.16 0.00 0.00 66.30
Average: 22 3.58 0.00 15.15 10.66 0.00
0.00 3.51 0.00 0.00 67.11
Average: 23 3.34 0.00 15.36 10.63 0.00
0.00 4.17 0.00 0.00 66.50
Average: 24 3.50 0.00 14.58 10.93 0.00
0.00 3.85 0.00 0.00 67.13
Average: 25 3.20 0.00 14.68 10.86 0.00
0.00 4.31 0.00 0.00 66.95
Average: 26 3.27 0.00 14.80 10.70 0.00
0.00 3.68 0.00 0.00 67.55
Average: 27 3.58 0.00 15.36 10.80 0.00
0.00 3.79 0.00 0.00 66.48
Average: 28 3.46 0.00 15.17 10.46 0.00
0.00 3.32 0.00 0.00 67.59
Average: 29 3.34 0.00 14.42 10.72 0.00
0.00 3.34 0.00 0.00 68.18
Average: 30 3.34 0.00 15.08 10.70 0.00
0.00 3.89 0.00 0.00 66.99
Average: 31 3.26 0.00 15.33 10.47 0.00
0.00 3.33 0.00 0.00 67.61
Average: 32 3.21 0.00 14.80 10.61 0.00
0.00 3.70 0.00 0.00 67.67
Average: 33 3.40 0.00 13.88 10.55 0.00
0.00 4.02 0.00 0.00 68.15
Average: 34 3.74 0.00 17.41 10.61 0.00
0.00 4.51 0.00 0.00 63.73
Average: 35 3.35 0.00 14.37 10.74 0.00
0.00 3.84 0.00 0.00 67.71
Average: 36 0.54 0.00 1.77 0.00 0.00
0.00 0.00 0.00 0.00 97.69
..
Average: 54 3.60 0.00 15.17 10.39 0.00
0.00 4.22 0.00 0.00 66.62
Average: 55 3.33 0.00 14.85 10.55 0.00
0.00 3.96 0.00 0.00 67.31
Average: 56 3.40 0.00 15.19 10.54 0.00
0.00 3.74 0.00 0.00 67.13
Average: 57 3.41 0.00 13.98 10.78 0.00
0.00 4.10 0.00 0.00 67.73
Average: 58 3.32 0.00 15.16 10.52 0.00
0.00 4.01 0.00 0.00 66.99
Average: 59 3.17 0.00 15.80 10.35 0.00
0.00 3.86 0.00 0.00 66.80
Average: 60 3.00 0.00 14.63 10.59 0.00
0.00 3.97 0.00 0.00 67.80
Average: 61 3.34 0.00 14.70 10.66 0.00
0.00 4.32 0.00 0.00 66.97
Average: 62 3.34 0.00 15.29 10.56 0.00
0.00 3.89 0.00 0.00 66.92
Average: 63 3.29 0.00 14.51 10.72 0.00
0.00 3.85 0.00 0.00 67.62
Average: 64 3.48 0.00 15.31 10.65 0.00
0.00 3.97 0.00 0.00 66.60
Average: 65 3.34 0.00 14.36 10.80 0.00
0.00 4.11 0.00 0.00 67.39
Average: 66 3.13 0.00 14.94 10.70 0.00
0.00 4.10 0.00 0.00 67.13
Average: 67 3.06 0.00 15.56 10.69 0.00
0.00 3.82 0.00 0.00 66.88
Average: 68 3.33 0.00 14.98 10.61 0.00
0.00 3.81 0.00 0.00 67.27
Average: 69 3.20 0.00 15.43 10.70 0.00
0.00 3.82 0.00 0.00 66.85
Average: 70 3.34 0.00 17.14 10.59 0.00
0.00 3.00 0.00 0.00 65.92
Average: 71 3.41 0.00 14.94 10.56 0.00
0.00 3.41 0.00 0.00 67.69

Perf top -

64.33% [kernel] [k] bt_iter
4.86% [kernel] [k] blk_mq_queue_tag_busy_iter
4.23% [kernel] [k] _find_next_bit
2.40% [kernel] [k] native_queued_spin_lock_slowpath
1.09% [kernel] [k] sbitmap_any_bit_set
0.71% [kernel] [k] sbitmap_queue_clear
0.63% [kernel] [k] find_next_bit
0.54% [kernel] [k] _raw_spin_lock_irqsave

>
>
> Thanks,
> Ming