From: John Garry <firstname.lastname@example.org> To: Ming Lei <email@example.com>, "chenxiang (M)" <firstname.lastname@example.org> Cc: Jens Axboe <email@example.com>, <firstname.lastname@example.org>, "Bart Van Assche" <email@example.com>, Hannes Reinecke <firstname.lastname@example.org>, "Christoph Hellwig" <email@example.com>, Thomas Gleixner <firstname.lastname@example.org>, Keith Busch <email@example.com> Subject: Re: [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug Date: Thu, 28 Nov 2019 10:45:49 +0000 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <20191128020205.GB3277@ming.t460p> On 28/11/2019 02:02, Ming Lei wrote: > On Thu, Nov 28, 2019 at 09:09:13AM +0800, chenxiang (M) wrote: >> Hi, >> >> 在 2019/10/14 9:50, Ming Lei 写道: >>> 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. >> >> I tested those patchset with John's testcase, except dump_stack() in >> function __blk_mq_run_hw_queue() sometimes occurs which don't >> affect the function, it solves the CPU hotplug issue, so add tested-by for >> those patchset: >> >> Tested-by: Xiang Chen <email@example.com> > > Thanks for your test. So I had to give up testing as my board experienced some SCSI timeout even without hotplugging or including this patchset. FWIW, I did test NVMe successfully though. > > I plan to post a new version for 5.6 cycle, and there is still some > small race window related with requeue to be covered. > thanks! > Thanks, > Ming > > . >
prev parent reply other threads:[~2019-11-28 10:46 UTC|newest] Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-14 1:50 Ming Lei 2019-10-14 1:50 ` [PATCH V4 1/5] blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED Ming Lei 2019-10-14 1:50 ` [PATCH V4 2/5] blk-mq: prepare for draining IO when hctx's all CPUs are offline Ming Lei 2019-10-14 1:50 ` [PATCH V4 3/5] blk-mq: stop to handle IO and drain IO before hctx becomes dead Ming Lei 2019-11-28 9:29 ` John Garry 2019-10-14 1:50 ` [PATCH V4 4/5] blk-mq: re-submit IO in case that hctx is dead Ming Lei 2019-10-14 1:50 ` [PATCH V4 5/5] blk-mq: handle requests dispatched from IO scheduler " Ming Lei 2019-10-16 8:58 ` [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug John Garry 2019-10-16 12:07 ` Ming Lei 2019-10-16 16:19 ` John Garry [not found] ` <firstname.lastname@example.org> 2019-10-20 10:14 ` Ming Lei 2019-10-21 9:19 ` John Garry 2019-10-21 9:34 ` Ming Lei 2019-10-21 9:47 ` John Garry 2019-10-21 10:24 ` Ming Lei 2019-10-21 11:49 ` John Garry 2019-10-21 12:53 ` Ming Lei 2019-10-21 14:02 ` John Garry 2019-10-22 0:16 ` Ming Lei 2019-10-22 11:19 ` John Garry 2019-10-22 13:45 ` Ming Lei 2019-10-25 16:33 ` John Garry 2019-10-28 10:42 ` Ming Lei 2019-10-28 11:55 ` John Garry 2019-10-29 1:50 ` Ming Lei 2019-10-29 9:22 ` John Garry 2019-10-29 10:05 ` Ming Lei 2019-10-29 17:54 ` John Garry 2019-10-31 16:28 ` John Garry 2019-11-28 1:09 ` chenxiang (M) 2019-11-28 2:02 ` Ming Lei 2019-11-28 10:45 ` John Garry [this message]
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