On Wed, Oct 16, 2019 at 09:58:27AM +0100, John Garry wrote:
> On 14/10/2019 02:50, Ming Lei wrote:
> > Hi,
> >
> > Thomas mentioned:
> > "
> > That was the constraint of managed interrupts from the very beginning:
> >
> > The driver/subsystem has to quiesce the interrupt line and the associated
> > queue _before_ it gets shutdown in CPU unplug and not fiddle with it
> > until it's restarted by the core when the CPU is plugged in again.
> > "
> >
> > But no drivers or blk-mq do that before one hctx becomes dead(all
> > CPUs for one hctx are offline), and even it is worse, blk-mq stills tries
> > to run hw queue after hctx is dead, see blk_mq_hctx_notify_dead().
> >
> > This patchset tries to address the issue by two stages:
> >
> > 1) add one new cpuhp state of CPUHP_AP_BLK_MQ_ONLINE
> >
> > - mark the hctx as internal stopped, and drain all in-flight requests
> > if the hctx is going to be dead.
> >
> > 2) re-submit IO in the state of CPUHP_BLK_MQ_DEAD after the hctx becomes dead
> >
> > - steal bios from the request, and resubmit them via generic_make_request(),
> > then these IO will be mapped to other live hctx for dispatch
> >
> > Please comment & review, thanks!
> >
> > John, I don't add your tested-by tag since V3 have some changes,
> > and I appreciate if you may run your test on V3.
>
> Hi Ming,
>
> So I got around to doing some testing. The good news is that issue which we
> were experiencing in v3 series seems to have has gone away - alot more
> stable.
>
> However, unfortunately, I did notice some SCSI timeouts:
>
> 15508.615074] CPU2: shutdown
> [15508.617778] psci: CPU2 killed.
> [15508.651220] CPU1: shutdown
> [15508.653924] psci: CPU1 killed.
> [15518.406229] sas: Enter sas_scsi_recover_host busy: 63 failed: 63
> Jobs: 1 (f=1): [R] [0.0% done] [0[15518.412239] sas: sas_scsi_find_task:
> aborting task 0x00000000a7159744
> KB/0KB/0KB /s] [0/0/0 iops] [eta [15518.421708] sas:
> sas_eh_handle_sas_errors: task 0x00000000a7159744 is done
> [15518.431266] sas: sas_scsi_find_task: aborting task 0x00000000d39731eb
> [15518.442539] sas: sas_eh_handle_sas_errors: task 0x00000000d39731eb is
> done
> [15518.449407] sas: sas_scsi_find_task: aborting task 0x000000009f77c9bd
> [15518.455899] sas: sas_eh_handle_sas_errors: task 0x000000009f77c9bd is
> done
>
> A couple of things to note:
> - I added some debug prints in blk_mq_hctx_drain_inflight_rqs() for when
> inflights rqs !=0, and I don't see them for this timeout
> - 0 datarate reported from fio
>
> I'll have a look...
What is the output of the following command?
(cd /sys/kernel/debug/block/$SAS_DISK && find . -type f -exec grep -aH . {} \;)
Thanks,
Ming
