Re: blk-mq 5-8 times slower for bmap-tools

[Ming Lei <ming.lei@redhat.com>]

On Mon, Aug 20, 2018 at 11:56:26AM +0200, Ricardo Ribalda Delgado wrote:
> Hi
> On Mon, Aug 20, 2018 at 11:55 AM Ming Lei <ming.lei@redhat.com> wrote:
> >
> > On Mon, Aug 20, 2018 at 11:04:08AM +0200, Ricardo Ribalda Delgado wrote:
> > > Hello Ming
> > > On Mon, Aug 20, 2018 at 10:30 AM Ming Lei <ming.lei@redhat.com> wrote:
> > > >
> > > > On Mon, Aug 20, 2018 at 09:39:45AM +0200, Ricardo Ribalda Delgado wrote:
> > > > > Some measurements:
> > > > >
> > > > > Please note that even when iostat shows 0.0 the LED on the device was
> > > > > blinking as if there was some activity going on.
> > > > >
> > > > > Thanks!
> > > > >
> > > > > KERNEL:
> > > > > Linux neopili 4.17.0-1-amd64 #1 SMP Debian 4.17.8-1 (2018-07-20)
> > > > > x86_64 GNU/Linux
> > > > >
> > > > > DISK:
> > > > > [247530.712686] usb 2-2: new SuperSpeed USB device number 3 using xhci_hcd
> > > > > [247530.738906] usb 2-2: New USB device found, idVendor=174c,
> > > > > idProduct=5136, bcdDevice= 1.00
> > > > > [247530.738913] usb 2-2: New USB device strings: Mfr=2, Product=3,
> > > > > SerialNumber=1
> > > > > [247530.738918] usb 2-2: Product: 91686
> > > > > [247530.738921] usb 2-2: Manufacturer: Delock
> > > > > [247530.738925] usb 2-2: SerialNumber: 300000003B45
> > > > > [247530.750709] scsi host6: uas
> > > > > [247530.751377] scsi 6:0:0:0: Direct-Access     ASMT     2105
> > > > >    0    PQ: 0 ANSI: 6
> > > > > [247530.752174] sd 6:0:0:0: Attached scsi generic sg2 type 0
> > > > > [247530.752616] sd 6:0:0:0: [sdb] 31277232 512-byte logical blocks:
> > > > > (16.0 GB/14.9 GiB)
> > > > > [247530.752740] sd 6:0:0:0: [sdb] Write Protect is off
> > > > > [247530.752742] sd 6:0:0:0: [sdb] Mode Sense: 43 00 00 00
> > > > > [247530.752905] sd 6:0:0:0: [sdb] Write cache: enabled, read cache:
> > > > > enabled, doesn't support DPO or FUA
> > > > > [247530.755912]  sdb: sdb1 sdb2
> > > > > [247530.756832] sd 6:0:0:0: [sdb] Attached SCSI disk
> > > > >
> > > > >
> > > > > TL/DR:
> > > > > CFQ: 21.7
> > > > > NOOP: 21.7
> > > > > DEADLINE: 21.7
> > > > > MQ-DEADLINE: 175.2
> > > > > NONE: 236.4
> > > > > KYBER: 174.9
> > > >
> > > > Thanks for your test!
> > > >
> > > > One problem found from your iostat log is that looks there is ~30sec
> > > > idle period between IO activities when blk-mq is enabled.
> > >
> > > During all the test the LED on the device was blinking.
> > >
> > > But a closer look to dmesg reveals a lot of this messages:
> > >
> > > [  196.929811] sd 6:0:0:0: [sdb] tag#3 data cmplt err -71 uas-tag 1
> > > inflight: CMD
> >
> > -71 is -EPROTO, which is returned from xhci driver, usually it means
> > there is error from the USB device side.
> >
> > > [  196.929822] sd 6:0:0:0: [sdb] tag#3 CDB: Write(10) 2a 00 00 04 00
> > > 68 00 04 00 00
> > > [  227.764379] sd 6:0:0:0: [sdb] tag#4 uas_eh_abort_handler 0 uas-tag
> > > 2 inflight: CMD OUT
> > > [  227.764389] sd 6:0:0:0: [sdb] tag#4 CDB: Write(10) 2a 00 00 04 04
> > > 68 00 04 00 00
> > > [  227.766555] sd 6:0:0:0: [sdb] tag#3 uas_eh_abort_handler 0 uas-tag
> > > 1 inflight: CMD
> > > [  227.766562] sd 6:0:0:0: [sdb] tag#3 CDB: Write(10) 2a 00 00 04 00
> > > 68 00 04 00 00
> > > [  227.784312] scsi host6: uas_eh_device_reset_handler start
> > > [  227.913672] usb 2-2: reset SuperSpeed USB device number 3 using xhci_hcd
> > > [  227.944842] scsi host6: uas_eh_device_reset_handler success
> > > [  231.416133] sd 6:0:0:0: [sdb] tag#1 data cmplt err -71 uas-tag 10
> > > inflight: CMD
> > > [  231.416147] sd 6:0:0:0: [sdb] tag#1 CDB: Write(10) 2a 00 00 06 d5
> > > e8 00 04 00 00
> > >
> > > And they take around 30 secons (227-196)
> > >
> > >
> > > Maybe this is a hw issue? I will bring the reader home tonight and see
> > > if I can replicate the bug with my notebook
> >
> > It might be.
> >
> > Is there such message in case of non-blk-mq?
> 
> No, only with blk-mq

OK, seems something doesn't work as expected in either scsi_mq or uas
driver.

Thanks,
Ming