From: Ming Lei <ming.lei@redhat.com>
To: John Garry <john.garry@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Bart Van Assche <bvanassche@acm.org>,
Hannes Reinecke <hare@suse.com>, Christoph Hellwig <hch@lst.de>,
Thomas Gleixner <tglx@linutronix.de>,
Keith Busch <keith.busch@intel.com>
Subject: Re: [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug
Date: Sun, 20 Oct 2019 18:14:08 +0800 [thread overview]
Message-ID: <20191020101404.GA5103@ming.t460p> (raw)
In-Reply-To: <55a84ea3-647d-0a76-596c-c6c6b2fc1b75@huawei.com>
On Thu, Oct 17, 2019 at 04:40:12PM +0100, John Garry wrote:
> On 16/10/2019 17:19, John Garry wrote:
> > 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.
> >
>
> I finally got to capture that debugfs dump at the point the SCSI IOs
> timeout, as attached. Let me know if any problem receiving it.
>
> Here's a kernel log snippet at that point (I added some print for the
> timeout):
>
> 609] psci: CPU6 killed.
> [ 547.722217] CPU5: shutdown
> [ 547.724926] psci: CPU5 killed.
> [ 547.749951] irq_shutdown
> [ 547.752701] IRQ 800: no longer affine to CPU4
> [ 547.757265] CPU4: shutdown
> [ 547.759971] psci: CPU4 killed.
> [ 547.790348] CPU3: shutdown
> [ 547.793052] psci: CPU3 killed.
> [ 547.818330] CPU2: shutdown
> [ 547.821033] psci: CPU2 killed.
> [ 547.854285] CPU1: shutdown
> [ 547.856989] psci: CPU1 killed.
> [ 575.925307] scsi_timeout req=0xffff0023b0dd9c00 reserved=0
> [ 575.930794] scsi_timeout req=0xffff0023b0df2700 reserved=0
From the debugfs log, 66 requests are dumped, and 63 of them has
been submitted to device, and the other 3 is in ->dispatch list
via requeue after timeout is handled.
You mentioned that:
" - 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"
There might be two reasons:
1) You are still testing a multiple reply-queue device? As I
mentioned last times, it is hard to map reply-queue into blk-mq
hctx correctly.
2) concurrent dispatch to device, which can be observed by the
following patch.
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 06081966549f..3590f6f947eb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -679,6 +679,8 @@ void blk_mq_start_request(struct request *rq)
{
struct request_queue *q = rq->q;
+ WARN_ON_ONCE(test_bit(BLK_MQ_S_INTERNAL_STOPPED, &rq->mq_hctx->state));
+
trace_block_rq_issue(q, rq);
if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
However, I think it is hard to be 2#, since the current CPU is the last
CPU in hctx->cpu_mask.
Thanks,
Ming
next prev parent reply other threads:[~2019-10-20 10:14 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-14 1:50 [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug 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] ` <55a84ea3-647d-0a76-596c-c6c6b2fc1b75@huawei.com>
2019-10-20 10:14 ` Ming Lei [this message]
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
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