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From: Ming Lei <ming.lei@redhat.com>
To: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: John Garry <john.garry@huawei.com>,
	linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Jens Axboe <axboe@kernel.dk>,
	Douglas Gilbert <dgilbert@interlog.com>
Subject: Re: [bug report] shared tags causes IO hang and performance drop
Date: Wed, 14 Apr 2021 19:12:57 +0800	[thread overview]
Message-ID: <YHbOOfGNHwO4SMS7@T590> (raw)
In-Reply-To: <cb326d404c6e0785d03a7dfadc42832c@mail.gmail.com>

On Wed, Apr 14, 2021 at 04:12:22PM +0530, Kashyap Desai wrote:
> > Hi Ming,
> >
> > >
> > > It is reported inside RH that CPU utilization is increased ~20% when
> > > running simple FIO test inside VM which disk is built on image stored
> > > on XFS/megaraid_sas.
> > >
> > > When I try to investigate by reproducing the issue via scsi_debug, I
> > > found IO hang when running randread IO(8k, direct IO, libaio) on
> > > scsi_debug disk created by the following command:
> > >
> > > 	modprobe scsi_debug host_max_queue=128
> > submit_queues=$NR_CPUS
> > > virtual_gb=256
> > >
> >
> > So I can recreate this hang for using mq-deadline IO sched for scsi debug,
> > in
> > that fio does not exit. I'm using v5.12-rc7.
> 
> I can also recreate this issue using mq-deadline. Using <none>, there is no
> IO hang issue.
> Also if I run script to change scheduler periodically (none, mq-deadline),
> sysfs entry hangs.
> 
> Here is call trace-
> Call Trace:
> [ 1229.879862]  __schedule+0x29d/0x7a0
> [ 1229.879871]  schedule+0x3c/0xa0
> [ 1229.879875]  blk_mq_freeze_queue_wait+0x62/0x90
> [ 1229.879880]  ? finish_wait+0x80/0x80
> [ 1229.879884]  elevator_switch+0x12/0x40
> [ 1229.879888]  elv_iosched_store+0x79/0x120
> [ 1229.879892]  ? kernfs_fop_write_iter+0xc7/0x1b0
> [ 1229.879897]  queue_attr_store+0x42/0x70
> [ 1229.879901]  kernfs_fop_write_iter+0x11f/0x1b0
> [ 1229.879905]  new_sync_write+0x11f/0x1b0
> [ 1229.879912]  vfs_write+0x184/0x250
> [ 1229.879915]  ksys_write+0x59/0xd0
> [ 1229.879917]  do_syscall_64+0x33/0x40
> [ 1229.879922]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> 
> I tried both - 5.12.0-rc1 and 5.11.0-rc2+ and there is a same behavior.
> Let me also check  megaraid_sas and see if anything generic or this is a
> special case of scsi_debug.

As I mentioned, it could be one generic issue wrt. SCHED_RESTART.
shared tags might have to restart all hctx since all share same tags.


Thanks,
Ming


  reply	other threads:[~2021-04-14 11:13 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-14  7:50 [bug report] shared tags causes IO hang and performance drop Ming Lei
2021-04-14 10:10 ` John Garry
2021-04-14 10:38   ` Ming Lei
2021-04-14 10:42   ` Kashyap Desai
2021-04-14 11:12     ` Ming Lei [this message]
2021-04-14 12:06       ` John Garry
2021-04-15  3:46         ` Ming Lei
2021-04-15 10:41           ` John Garry
2021-04-15 12:18             ` Ming Lei
2021-04-15 15:41               ` John Garry
2021-04-16  0:46                 ` Ming Lei
2021-04-16  8:29                   ` John Garry
2021-04-16  8:39                     ` Ming Lei
2021-04-16 14:59                       ` John Garry
2021-04-20  3:06                         ` Douglas Gilbert
2021-04-20  3:22                           ` Bart Van Assche
2021-04-20  4:54                             ` Douglas Gilbert
2021-04-20  6:52                               ` Ming Lei
2021-04-20 20:22                                 ` Douglas Gilbert
2021-04-21  1:40                                   ` Ming Lei
2021-04-23  8:43           ` John Garry
2021-04-26 10:53             ` John Garry
2021-04-26 14:48               ` Ming Lei
2021-04-26 15:52                 ` John Garry
2021-04-26 16:03                   ` Ming Lei
2021-04-26 17:02                     ` John Garry
2021-04-26 23:59                       ` Ming Lei
2021-04-27  7:52                         ` John Garry
2021-04-27  9:11                           ` Ming Lei
2021-04-27  9:37                             ` John Garry
2021-04-27  9:52                               ` Ming Lei
2021-04-27 10:15                                 ` John Garry
2021-07-07 17:06                                 ` John Garry
2021-04-14 13:59       ` Kashyap Desai
2021-04-14 17:03         ` Douglas Gilbert
2021-04-14 18:19           ` John Garry
2021-04-14 19:39             ` Douglas Gilbert
2021-04-15  0:58         ` Ming Lei

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