On 5/8/20 3:49 PM, Ming Lei wrote: > On Tue, May 05, 2020 at 10:09:19AM +0800, 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 inactive(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 >> >> Thanks John Garry for running lots of tests on arm64 with this patchset >> and co-working on investigating all kinds of issues. >> >> Thanks Christoph's review on V7 & V8. >> >> Please comment & review, thanks! >> >> https://github.com/ming1/linux/commits/v5.7-rc-blk-mq-improve-cpu-hotplug >> >> V10: >> - fix double bio complete in request resubmission(10/11) >> - add tested-by tag >> >> V9: >> - add Reviewed-by tag >> - document more on memory barrier usage between getting driver tag >> and handling cpu offline(7/11) >> - small code cleanup as suggested by Chritoph(7/11) >> - rebase against for-5.8/block(1/11, 2/11) >> V8: >> - add patches to share code with blk_rq_prep_clone >> - code re-organization as suggested by Christoph, most of them are >> in 04/11, 10/11 >> - add reviewed-by tag >> >> V7: >> - fix updating .nr_active in get_driver_tag >> - add hctx->cpumask check in cpuhp handler >> - only drain requests which tag is >= 0 >> - pass more aggressive cpuhotplug&io test >> >> V6: >> - simplify getting driver tag, so that we can drain in-flight >> requests correctly without using synchronize_rcu() >> - handle re-submission of flush & passthrough request correctly >> >> V5: >> - rename BLK_MQ_S_INTERNAL_STOPPED as BLK_MQ_S_INACTIVE >> - re-factor code for re-submit requests in cpu dead hotplug handler >> - address requeue corner case >> >> 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 (11): >> block: clone nr_integrity_segments and write_hint in blk_rq_prep_clone >> block: add helper for copying request >> blk-mq: mark blk_mq_get_driver_tag as static >> blk-mq: assign rq->tag in blk_mq_get_driver_tag >> blk-mq: support rq filter callback when iterating rqs >> 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 inactive >> block: add blk_end_flush_machinery >> blk-mq: add blk_mq_hctx_handle_dead_cpu for handling cpu dead >> blk-mq: re-submit IO in case that hctx is inactive >> block: deactivate hctx when the hctx is actually inactive >> >> block/blk-core.c | 27 ++- >> block/blk-flush.c | 141 ++++++++++++--- >> block/blk-mq-debugfs.c | 2 + >> block/blk-mq-tag.c | 39 ++-- >> block/blk-mq-tag.h | 4 + >> block/blk-mq.c | 356 +++++++++++++++++++++++++++++-------- >> block/blk-mq.h | 22 ++- >> block/blk.h | 11 +- >> drivers/block/loop.c | 2 +- >> drivers/md/dm-rq.c | 2 +- >> include/linux/blk-mq.h | 6 + >> include/linux/cpuhotplug.h | 1 + >> 12 files changed, 481 insertions(+), 132 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> > > Hi Jens, > > This patches have been worked and discussed for a while, so any chance > to make it in 5.8 if no any further comments? Looks like we're pretty close, I'll take a closer look at v11 when posted. -- Jens Axboe
