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

[Ben Hutchings <ben@decadent.org.uk>]

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On Mon, 2018-08-20 at 11:04 +0200, Ricardo Ribalda Delgado wrote:
> Hello Ming
> On Mon, Aug 20, 2018 at 10:30 AM Ming Lei <ming.lei@redhat.com> wrote:
[...]
> > 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
> [  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
> 
> > 
> > Maybe it is related with timeout, given we had big change in v4.17 timeout code,
> > and we also fixed one scsi_mq timeout related issue recently, and the patch[1] has
> > been merged to v4.18 release already.
> 
> I tried with v4.18-rc4 (latest one packaged in debian experimental)
> and after 3 runs, 2 were fine (27 sec), but the last one was over a
> minute.

Is it possible that this is fixed by "block: really disable runtime-pm
for blk-mq"?

That fix went into Debian's version 4.17.14-1, but is not yet in any
4.18-based package.

Ben.

-- 
Ben Hutchings
You can't have everything.  Where would you put it?


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