On 16/10/2019 13:07, Ming Lei wrote:
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 . {} \;)
I assume that you want this run at about the time SCSI EH kicks in for
the timeout, right? If so, I need to find some simple sysfs entry to
tell me of this occurrence, to trigger the capture. Or add something. My
script is pretty dump.
BTW, I did notice that we the dump_stack in __blk_mq_run_hw_queue()
pretty soon before the problem happens - maybe a clue or maybe coincidence.
Thanks,
John
Thanks,
Ming
.
