High IO load cause kswapd hang and unresponsive system

Sun Nov 18 10:40:23 EST 2018

On Sat, Nov 17, 2018 at 4:36 PM Naruto Nguyen <narutonguyen2018 at gmail.com>
wrote:

> Hi Mulyadi,
>
> Thanks for your answer. I have updated to kernel 4.4.121 but the issue
> still exists. I will try to update to kernel 4.4.163. But if you could
> provide any reason that why i did not see the issue in the 3.12 kernel and
> now it happens in 4.4, any changes in 4.4 can trigger the issue? And if
> kernel 4.4.163 has any changes to fix the issue?
>
>
Hi..

Please don't top post.

As for the "why", that I don't know. There are too many changes between 3.x
and 4.x. That's why checking if the issue still happens with latest stable
version IS the first logical step .

> Thanks,
> Naruto
>
> On Friday, 16 November 2018, Mulyadi Santosa <mulyadi.santosa at gmail.com>
> wrote:
>
>>
>>
>> On Thu, Nov 15, 2018 at 11:57 PM Naruto Nguyen <
>> narutonguyen2018 at gmail.com> wrote:
>>
>>> Hi everyone,
>>>
>>> Recently when I upgrade my kernel from 3.12.61 to kernel 4.4.74, I
>>>
>>
>> Hi.
>>
>> You need to upgrade, either using 4.19.2, 4.18.2, or 4.4.163 (if you
>> prefer to stay with 4.4.x) and see if it still happens
>>
>> find my system sometimes is very slow and unresponsive
>>>
>>> When my system is under a heavy IO load, I see the node start to
>>> respond very slow, the IO wait time keeps very high, and the node
>>> starts unresponsive. I try to dump all block task at that time and
>>> found some interesting things, look like under a heavy load I/O, the
>>> kswap start to hang in jbd2_log_wait_commit.
>>>
>>> Sep 07 12:25:35 myPC kernel: [11039.126514] kswapd0         D
>>> 0000000000000000     0    26      2 0x00000000
>>> Sep 07 12:25:35 myPC kernel: [11039.126517]  ffff88003da27b78
>>> ffff88000ce08280 ffff88003cdf0680 ffff88003da28000
>>> Sep 07 12:25:35 myPC kernel: [11039.126519]  ffff88001a15c888
>>> ffff88001a15c824 ffff88003da27bb8 ffff88001a15c8a0
>>> Sep 07 12:25:35 myPC kernel: [11039.126521]  ffff88003da27b90
>>> ffffffff815e4c85 ffff88001a15c800 0000000000013183
>>> Sep 07 12:25:35 myPC kernel: [11039.126522] Call Trace:
>>> Sep 07 12:25:35 myPC kernel: [11039.126539]  [<ffffffff815e4c85>]
>>> schedule+0x35/0x80
>>> Sep 07 12:25:35 myPC kernel: [11039.126561]  [<ffffffffa02faada>]
>>> jbd2_log_wait_commit+0x8a/0xf0 [jbd2]
>>> Sep 07 12:25:35 myPC kernel: [11039.126621]  [<ffffffffa03b28a4>]
>>> ext4_evict_inode+0x2d4/0x4b0 [ext4]
>>> Sep 07 12:25:35 myPC kernel: [11039.126630]  [<ffffffff81215a7a>]
>>> evict+0xba/0x190
>>> Sep 07 12:25:35 myPC kernel: [11039.126635]  [<ffffffff81215b82>]
>>> dispose_list+0x32/0x50
>>> Sep 07 12:25:35 myPC kernel: [11039.126639]  [<ffffffff81216e52>]
>>> prune_icache_sb+0x42/0x50
>>> Sep 07 12:25:35 myPC kernel: [11039.126644]  [<ffffffff811ff8f6>]
>>> super_cache_scan+0x136/0x180
>>> Sep 07 12:25:35 myPC kernel: [11039.126653]  [<ffffffff81196a1b>]
>>> shrink_slab.part.41+0x20b/0x3f0
>>> Sep 07 12:25:35 myPC kernel: [11039.126521]  ffff88003da27b90
>>> ffffffff815e4c85 ffff88001a15c800 0000000000013183
>>>
>>> And after that more and more processes are hitting STAT D, nfsd is
>>> hang to wait or the inode deletion to complete in
>>> __wait_on_freeing_inode.
>>>
>>> Sep 07 12:25:35 myPC kernel: [11039.390218] nfsd            D
>>> 0000000000000000     0 30419      2 0x00000080
>>> Sep 07 12:25:35 myPC kernel: [11039.390221]  ffff88000da47a98
>>> ffff8800277ec380 ffff8800374ec580 ffff88000da48000
>>> Sep 07 12:25:35 myPC kernel: [11039.390223]  ffff88000da47ad8
>>> ffffc9000011edc8 0000000000000000 ffff88000e92e2f8
>>> Sep 07 12:25:35 myPC kernel: [11039.390225]  ffff88000da47ab0
>>> ffffffff815e4c85 ffffffff81c094c0 ffff88003ff9d8b8
>>> Sep 07 12:25:35 myPC kernel: [11039.390225] Call Trace:
>>> Sep 07 12:25:35 myPC kernel: [11039.390231]  [<ffffffff815e4c85>]
>>> schedule+0x35/0x80
>>> Sep 07 12:25:35 myPC kernel: [11039.390236]  [<ffffffff812157fc>]
>>> __wait_on_freeing_inode+0x9c/0xc0
>>> Sep 07 12:25:35 myPC kernel: [11039.390241]  [<ffffffff81215d83>]
>>> find_inode_fast+0x73/0xa0
>>> Sep 07 12:25:35 myPC kernel: [11039.390245]  [<ffffffff81216052>]
>>> iget_locked+0x72/0x190
>>> Sep 07 12:25:35 myPC kernel: [11039.390284]  [<ffffffffa03aeb8c>]
>>> ext4_iget+0x2c/0xb10 [ext4]
>>> Sep 07 12:25:35 myPC kernel: [11039.390314]  [<ffffffffa03c1055>]
>>> ext4_nfs_get_inode+0x45/0x80 [ext4]
>>> Sep 07 12:25:35 myPC kernel: [11039.390320]  [<ffffffff812211c4>]
>>> generic_fh_to_dentry+0x24/0x30
>>> Sep 07 12:25:35 myPC kernel: [11039.390326]  [<ffffffff81277ede>]
>>> exportfs_decode_fh+0x5e/0x350
>>> Sep 07 12:25:35 myPC kernel: [11039.390347]  [<ffffffffa047749a>]
>>> fh_verify+0x2da/0x5a0 [nfsd]
>>> Sep 07 12:25:35 myPC kernel: [11039.390362]  [<ffffffffa0480933>]
>>> nfsd3_proc_getattr+0x63/0xd0 [nfsd]
>>> Sep 07 12:25:35 myPC kernel: [11039.390374]  [<ffffffffa0473e23>]
>>> nfsd_dispatch+0xc3/0x260 [nfsd]
>>> Sep 07 12:25:35 myPC kernel: [11039.390411]  [<ffffffffa0322108>]
>>> svc_process_common+0x418/0x6a0 [sunrpc]
>>> Sep 07 12:25:35 myPC kernel: [11039.390439]  [<ffffffffa032248d>]
>>> svc_process+0xfd/0x1b0 [sunrpc]
>>> Sep 07 12:25:35 myPC kernel: [11039.390454]  [<ffffffffa047389a>]
>>> nfsd+0xea/0x160 [nfsd]
>>>
>>> That causes the other nfs client is hang to wait nfsd to continue.
>>>
>>> Sep 07 12:25:35 myPC kernel: [11039.207987] Call Trace:
>>> Sep 07 12:25:35 myPC kernel: [11039.207994]  [<ffffffff815e4c85>]
>>> schedule+0x35/0x80
>>> Sep 07 12:25:35 myPC kernel: [11039.208008]  [<ffffffffa031acce>]
>>> rpc_wait_bit_killable+0x1e/0xa0 [sunrpc]
>>> Sep 07 12:25:35 myPC kernel: [11039.208055]  [<ffffffff815e5098>]
>>> __wait_on_bit+0x58/0x90
>>> Sep 07 12:25:35 myPC kernel: [11039.208059]  [<ffffffff815e513e>]
>>> out_of_line_wait_on_bit+0x6e/0x80
>>> Sep 07 12:25:35 myPC kernel: [11039.208082]  [<ffffffffa031bd26>]
>>> __rpc_execute+0x146/0x440 [sunrpc]
>>> Sep 07 12:25:35 myPC kernel: [11039.208104]  [<ffffffffa0313049>]
>>> rpc_run_task+0x69/0x80 [sunrpc]
>>> Sep 07 12:25:35 myPC kernel: [11039.208126]  [<ffffffffa031309f>]
>>> rpc_call_sync+0x3f/0xa0 [sunrpc]
>>> Sep 07 12:25:35 myPC kernel: [11039.204818]  [<ffffffff81200d69>]
>>> vfs_fstatat+0x49/0x90
>>> Sep 07 12:25:35 myPC kernel: [11039.204821]  [<ffffffff812011ea>]
>>> SYSC_newstat+0x1a/0x40
>>> Sep 07 12:25:35 myPC kernel: [11039.204826]  [<ffffffff815e876e>]
>>> entry_SYSCALL_64_fastpath+0x12/0x6d
>>> Sep 07 12:25:35 myPC kernel: [11039.207972] DWARF2 unwinder stuck at
>>> entry_SYSCALL_64_fastpath+0x12/0x6d
>>>
>>> I guess under heavy load, somehow the inode cannot be evicted in
>>> kswap, so the nfsd just keeps waiting and cause the whole system ends
>>> up in unresponsive state. I found some related issues
>>>
>>> https://www.systutorials.com/linux-kernels/105429/nfsv4-1-prevent-a-3-way-deadlock-between-layoutreturn-open-and-state-recovery-linux-3-12-17/
>>> (it’s not the same as it’s nfsv4 but just refer for the same symptom.)
>>>
>>> My system has very limited resource, only 1 core and  1GB RAM and the
>>> issue is very easy to happen in a slow disk. However, I did not see
>>> the same issue in the older kernel 3.12.61. Could you please let me
>>> know if my analysis makes sense, if jbd2_log_wait_commit hang causes
>>> __wait_on_freeing_inode wait ? Is it a known issue in kernel? If any
>>> kernel change causes the issue?. And if we have any WA to avoid that
>>> like preventing kswapd kicks in (I have a 5G swap partition) or to
>>> make my system is not unresponsive like that (of course it is not to
>>> add more RAM :) ?
>>>
>>> Thanks a lot
>>> Brs,
>>> Naruto
>>>
>>> _______________________________________________
>>> Kernelnewbies mailing list
>>> Kernelnewbies at kernelnewbies.org
>>> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>
>>
>>
>> --
>> regards,
>>
>> Mulyadi Santosa
>> Freelance Linux trainer and consultant
>>
>> blog: the-hydra.blogspot.com
>> training: mulyaditraining.blogspot.com
>>
>

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com
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