Re: [PATCH] blk-mq: only run mapped hw queues in blk_mq_run_hw_queues()

[Christian Borntraeger <borntraeger@de.ibm.com>]

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On 03/29/2018 01:43 PM, Ming Lei wrote:
> On Thu, Mar 29, 2018 at 12:49:55PM +0200, Christian Borntraeger wrote:
>>
>>
>> On 03/29/2018 12:48 PM, Ming Lei wrote:
>>> On Thu, Mar 29, 2018 at 12:10:11PM +0200, Christian Borntraeger wrote:
>>>>
>>>>
>>>> On 03/29/2018 11:40 AM, Ming Lei wrote:
>>>>> On Thu, Mar 29, 2018 at 11:09:08AM +0200, Christian Borntraeger wrote:
>>>>>>
>>>>>>
>>>>>> On 03/29/2018 09:23 AM, Christian Borntraeger wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 03/29/2018 04:00 AM, Ming Lei wrote:
>>>>>>>> On Wed, Mar 28, 2018 at 05:36:53PM +0200, Christian Borntraeger wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 03/28/2018 05:26 PM, Ming Lei wrote:
>>>>>>>>>> Hi Christian,
>>>>>>>>>>
>>>>>>>>>> On Wed, Mar 28, 2018 at 09:45:10AM +0200, Christian Borntraeger wrote:
>>>>>>>>>>> FWIW, this patch does not fix the issue for me:
>>>>>>>>>>>
>>>>>>>>>>> ostname=? addr=? terminal=? res=success'
>>>>>>>>>>> [   21.454961] WARNING: CPU: 3 PID: 1882 at block/blk-mq.c:1410 __blk_mq_delay_run_hw_queue+0xbe/0xd8
>>>>>>>>>>> [   21.454968] Modules linked in: scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_mirror dm_region_hash dm_log dm_multipath dm_mod autofs4
>>>>>>>>>>> [   21.454984] CPU: 3 PID: 1882 Comm: dasdconf.sh Not tainted 4.16.0-rc7+ #26
>>>>>>>>>>> [   21.454987] Hardware name: IBM 2964 NC9 704 (LPAR)
>>>>>>>>>>> [   21.454990] Krnl PSW : 00000000c0131ea3 000000003ea2f7bf (__blk_mq_delay_run_hw_queue+0xbe/0xd8)
>>>>>>>>>>> [   21.454996]            R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
>>>>>>>>>>> [   21.455005] Krnl GPRS: 0000013abb69a000 0000013a00000000 0000013ac6c0dc00 0000000000000001
>>>>>>>>>>> [   21.455008]            0000000000000000 0000013abb69a710 0000013a00000000 00000001b691fd98
>>>>>>>>>>> [   21.455011]            00000001b691fd98 0000013ace4775c8 0000000000000001 0000000000000000
>>>>>>>>>>> [   21.455014]            0000013ac6c0dc00 0000000000b47238 00000001b691fc08 00000001b691fbd0
>>>>>>>>>>> [   21.455032] Krnl Code: 000000000069c596: ebaff0a00004	lmg	%r10,%r15,160(%r15)
>>>>>>>>>>>                           000000000069c59c: c0f4ffff7a5e	brcl	15,68ba58
>>>>>>>>>>>                          #000000000069c5a2: a7f40001		brc	15,69c5a4
>>>>>>>>>>>                          >000000000069c5a6: e340f0c00004	lg	%r4,192(%r15)
>>>>>>>>>>>                           000000000069c5ac: ebaff0a00004	lmg	%r10,%r15,160(%r15)
>>>>>>>>>>>                           000000000069c5b2: 07f4		bcr	15,%r4
>>>>>>>>>>>                           000000000069c5b4: c0e5fffffeea	brasl	%r14,69c388
>>>>>>>>>>>                           000000000069c5ba: a7f4fff6		brc	15,69c5a6
>>>>>>>>>>> [   21.455067] Call Trace:
>>>>>>>>>>> [   21.455072] ([<00000001b691fd98>] 0x1b691fd98)
>>>>>>>>>>> [   21.455079]  [<000000000069c692>] blk_mq_run_hw_queue+0xba/0x100 
>>>>>>>>>>> [   21.455083]  [<000000000069c740>] blk_mq_run_hw_queues+0x68/0x88 
>>>>>>>>>>> [   21.455089]  [<000000000069b956>] __blk_mq_complete_request+0x11e/0x1d8 
>>>>>>>>>>> [   21.455091]  [<000000000069ba9c>] blk_mq_complete_request+0x8c/0xc8 
>>>>>>>>>>> [   21.455103]  [<00000000008aa250>] dasd_block_tasklet+0x158/0x490 
>>>>>>>>>>> [   21.455110]  [<000000000014c742>] tasklet_hi_action+0x92/0x120 
>>>>>>>>>>> [   21.455118]  [<0000000000a7cfc0>] __do_softirq+0x120/0x348 
>>>>>>>>>>> [   21.455122]  [<000000000014c212>] irq_exit+0xba/0xd0 
>>>>>>>>>>> [   21.455130]  [<000000000010bf92>] do_IRQ+0x8a/0xb8 
>>>>>>>>>>> [   21.455133]  [<0000000000a7c298>] io_int_handler+0x130/0x298 
>>>>>>>>>>> [   21.455136] Last Breaking-Event-Address:
>>>>>>>>>>> [   21.455138]  [<000000000069c5a2>] __blk_mq_delay_run_hw_queue+0xba/0xd8
>>>>>>>>>>> [   21.455140] ---[ end trace be43f99a5d1e553e ]---
>>>>>>>>>>> [   21.510046] dasdconf.sh Warning: 0.0.241e is already online, not configuring
>>>>>>>>>>
>>>>>>>>>> Thinking about this issue further, I can't understand the root cause for
>>>>>>>>>> this issue.
>>>>>>
>>>>>> FWIW, Limiting CONFIG_NR_CPUS to 64 seems to make the problem go away.
>>>>>
>>>>> I think the following patch is needed, and this way aligns to the mapping
>>>>> created via managed IRQ at least.
>>>>>
>>>>> diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
>>>>> index 9f8cffc8a701..638ab5c11b3c 100644
>>>>> --- a/block/blk-mq-cpumap.c
>>>>> +++ b/block/blk-mq-cpumap.c
>>>>> @@ -14,13 +14,12 @@
>>>>>  #include "blk.h"
>>>>>  #include "blk-mq.h"
>>>>>
>>>>> +/*
>>>>> + * Given there isn't CPU hotplug handler in blk-mq, map all possible CPUs to
>>>>> + * queues even it isn't present yet.
>>>>> + */
>>>>>  static int cpu_to_queue_index(unsigned int nr_queues, const int cpu)
>>>>>  {
>>>>> -	/*
>>>>> -	 * Non present CPU will be mapped to queue index 0.
>>>>> -	 */
>>>>> -	if (!cpu_present(cpu))
>>>>> -		return 0;
>>>>>  	return cpu % nr_queues;
>>>>>  }
>>>>>
>>>>> Thanks,
>>>>> Ming
>>>>>
>>>>
>>>> With that I no longer see the WARN_ON but the other warning instead:
>>>>
>>>> [   31.903096] audit: type=1130 audit(1522318064.439:41): pid=1 uid=0 auid=4294967295 ses=4294967295 msg='unit=systemd-tmpfiles-setup-dev comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
>>>> [   31.903100] audit: type=1131 audit(1522318064.439:42): pid=1 uid=0 auid=4294967295 ses=4294967295 msg='unit=systemd-tmpfiles-setup-dev comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'
>>>> [   31.985756] systemd-journald[379]: Received SIGTERM from PID 1 (systemd).
>>>> [   32.000543] systemd: 18 output lines suppressed due to ratelimiting
>>>> [   32.209496] EXT4-fs (dasdc1): re-mounted. Opts: (null)
>>>> [   32.234808] systemd-journald[2490]: Received request to flush runtime journal from PID 1
>>>> [   32.359832] tun: Universal TUN/TAP device driver, 1.6
>>>> [   32.470841] run queue from wrong CPU 18, hctx active
>>>
>>> But your 'lscpu' log showed that you only have 16 CPUs online(0~15) and
>>> you also said CPU hotplug isn't involved in your test, so I am just
>>> wondering where the CPU 18 is from?
>>
>>
>> I have 2 test systems. One with 44CPU the other with 16.
>> The one  with 16 now has the same flood of messages:
>>
>>
>>     4.454510]  dasdc:VOL1/  0X3F77: dasdc1
>> [    4.454592]  dasdd:VOL1/  0X3F74: dasdd1
>> [    4.593711] run queue from wrong CPU 0, hctx active
> 
> Still can't reproduce your issue, could you please collect debugfs
> log again on your 16-core system after applying the patch on blk_mq_cpumap.c?

done.

If you need anything quick, you can reach mit via irc freenode or oftc (user borntraeger)

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