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...
Thanks,
John
V4:
- resubmit IOs in dispatch list in case that this hctx is dead
V3:
- re-organize patch 2 & 3 a bit for addressing Hannes's comment
- fix patch 4 for avoiding potential deadlock, as found by Hannes
V2:
- patch4 & patch 5 in V1 have been merged to block tree, so remove
them
- address comments from John Garry and Minwoo
Ming Lei (5):
blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED
blk-mq: prepare for draining IO when hctx's all CPUs are offline
blk-mq: stop to handle IO and drain IO before hctx becomes dead
blk-mq: re-submit IO in case that hctx is dead
blk-mq: handle requests dispatched from IO scheduler in case that hctx
is dead
block/blk-mq-debugfs.c | 2 +
block/blk-mq-tag.c | 2 +-
block/blk-mq-tag.h | 2 +
block/blk-mq.c | 137 ++++++++++++++++++++++++++++++++++---
block/blk-mq.h | 3 +-
drivers/block/loop.c | 2 +-
drivers/md/dm-rq.c | 2 +-
include/linux/blk-mq.h | 5 ++
include/linux/cpuhotplug.h | 1 +
9 files changed, 141 insertions(+), 15 deletions(-)
Cc: John Garry <john.garry@xxxxxxxxxx>
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
