Unfortunately the CentOS kernel (3.10.0-862.14.4.el7.x86_64) has issues as well.  Different ones, but the nodes end up with an unusable mount in an hour or two.  Here are some syslogs:

Oct  1 11:50:28 worker1004 kernel: INFO: task fio:29007 blocked for more than 120 seconds. Oct  1 11:50:28 worker1004 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Oct  1 11:50:28 worker1004 kernel: fio             D ffff996d86e92f70     0 29007  28970 0x00000000
Oct  1 11:50:28 worker1004 kernel: Call Trace:
Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c316ec0>] ? bit_wait+0x50/0x50
Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c318f39>] schedule+0x29/0x70
Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c3168a9>] schedule_timeout+0x239/0x2c0 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bcfa982>] ? ktime_get_ts64+0x52/0xf0
Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c316ec0>] ? bit_wait+0x50/0x50
Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c31844d>] io_schedule_timeout+0xad/0x130 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c3184e8>] io_schedule+0x18/0x20 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c316ed1>] bit_wait_io+0x11/0x50 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c316a81>] __wait_on_bit_lock+0x61/0xc0 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bd96684>] __lock_page+0x74/0x90 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bcbefd0>] ? wake_bit_function+0x40/0x40 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bd971a4>] __find_lock_page+0x54/0x70 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bd97ed5>] grab_cache_page_write_begin+0x55/0xc0 Oct  1 11:50:28 worker1004 kernel: [<ffffffffc12798e3>] ceph_write_begin+0x43/0xe0 [ceph] Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bd96ac4>] generic_file_buffered_write+0x124/0x2c0 Oct  1 11:50:28 worker1004 kernel: [<ffffffffc127526e>] ceph_aio_write+0xa3e/0xcb0 [ceph] Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bdc81be>] ? do_numa_page+0x1be/0x250 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bdc8566>] ? handle_pte_fault+0x316/0xd10 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8be731a3>] ? aio_read_events+0x1f3/0x2e0 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8bed5437>] ? security_file_permission+0x27/0xa0 Oct  1 11:50:28 worker1004 kernel: [<ffffffffc1274830>] ? ceph_direct_read_write+0xcd0/0xcd0 [ceph] Oct  1 11:50:28 worker1004 kernel: [<ffffffff8be74783>] do_io_submit+0x3c3/0x870 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8be74c40>] SyS_io_submit+0x10/0x20 Oct  1 11:50:28 worker1004 kernel: [<ffffffff8c32579b>] system_call_fastpath+0x22/0x27 Oct  1 11:52:28 worker1004 kernel: INFO: task fio:29007 blocked for more than 120 seconds. Oct  1 11:52:28 worker1004 kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Oct  1 11:52:28 worker1004 kernel: fio             D ffff996d86e92f70     0 29007  28970 0x00000000
Oct  1 11:52:28 worker1004 kernel: Call Trace:
Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c316ec0>] ? bit_wait+0x50/0x50
Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c318f39>] schedule+0x29/0x70
Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c3168a9>] schedule_timeout+0x239/0x2c0 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bcfa982>] ? ktime_get_ts64+0x52/0xf0
Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c316ec0>] ? bit_wait+0x50/0x50
Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c31844d>] io_schedule_timeout+0xad/0x130 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c3184e8>] io_schedule+0x18/0x20 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c316ed1>] bit_wait_io+0x11/0x50 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c316a81>] __wait_on_bit_lock+0x61/0xc0 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bd96684>] __lock_page+0x74/0x90 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bcbefd0>] ? wake_bit_function+0x40/0x40 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bd971a4>] __find_lock_page+0x54/0x70 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bd97ed5>] grab_cache_page_write_begin+0x55/0xc0 Oct  1 11:52:28 worker1004 kernel: [<ffffffffc12798e3>] ceph_write_begin+0x43/0xe0 [ceph] Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bd96ac4>] generic_file_buffered_write+0x124/0x2c0 Oct  1 11:52:28 worker1004 kernel: [<ffffffffc127526e>] ceph_aio_write+0xa3e/0xcb0 [ceph] Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bdc81be>] ? do_numa_page+0x1be/0x250 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bdc8566>] ? handle_pte_fault+0x316/0xd10 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8be731a3>] ? aio_read_events+0x1f3/0x2e0 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8bed5437>] ? security_file_permission+0x27/0xa0 Oct  1 11:52:28 worker1004 kernel: [<ffffffffc1274830>] ? ceph_direct_read_write+0xcd0/0xcd0 [ceph] Oct  1 11:52:28 worker1004 kernel: [<ffffffff8be74783>] do_io_submit+0x3c3/0x870 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8be74c40>] SyS_io_submit+0x10/0x20 Oct  1 11:52:28 worker1004 kernel: [<ffffffff8c32579b>] system_call_fastpath+0x22/0x27

Oct  1 15:04:08 worker1004 kernel: libceph: reset on mds0
Oct  1 15:04:08 worker1004 kernel: ceph: mds0 closed our session
Oct  1 15:04:08 worker1004 kernel: ceph: mds0 reconnect start
Oct  1 15:04:08 worker1004 kernel: libceph: osd182 10.128.150.155:6976 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd548 10.128.150.171:6936 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd59 10.128.150.154:6918 socket closed (con state OPEN)
Oct  1 15:04:08 worker1004 kernel: ceph: mds0 reconnect denied
Oct  1 15:04:08 worker1004 kernel: ceph:  dropping dirty+flushing Fw state for ffff997ff05193b0 1099516450605 Oct  1 15:04:08 worker1004 kernel: ceph:  dropping dirty+flushing Fw state for ffff997ff0519930 1099516450607 Oct  1 15:04:08 worker1004 kernel: ceph:  dropping dirty+flushing Fw state for ffff997ff051a430 1099516450606 Oct  1 15:04:08 worker1004 kernel: ceph:  dropping dirty+flushing Fw state for ffff997ff0519eb0 1099516450608 Oct  1 15:04:08 worker1004 kernel: libceph: osd356 10.128.150.31:6844 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd120 10.128.150.154:6885 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: mds0 10.130.134.4:6800 socket closed (con state NEGOTIATING) Oct  1 15:04:08 worker1004 kernel: libceph: osd151 10.128.150.155:6808 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd129 10.128.150.154:6845 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd363 10.128.150.31:6872 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd712 10.128.150.177:6908 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd592 10.128.150.174:6917 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd866 10.128.150.42:6976 socket error on write Oct  1 15:04:08 worker1004 kernel: libceph: osd395 10.128.150.158:6868 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd159 10.128.150.155:6952 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd901 10.128.150.43:6936 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd658 10.128.150.176:6946 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd422 10.128.150.159:6859 socket closed (con state OPEN) Oct  1 15:04:08 worker1004 kernel: libceph: osd718 10.128.150.177:6928 socket error on read
and similar.

These nodes have been rock solid stable with ceph-fuse 12.2.7.  They definitely have no known networking issues, and the ceph cluster was healthy during this time.  In the MDS logs there are no entries around the problematic times either.  And after all this, the mount is unusable:

[root@worker1004 ~]# ls -l /mnt/cephtest
ls: cannot access /mnt/cephtest: Permission denied

Andras


On 10/1/18 3:02 PM, Andras Pataki wrote:
These hangs happen during random I/O fio benchmark loads.  Something like 4 or 8 fio processes doing random reads/writes to distinct large files (to ensure there is no caching possible).  This is all on CentOS 7.4 nodes.  Same (and even tougher) tests run without any problems with ceph-fuse.  We do have jobs that do heavy parallel I/O (MPI-IO, HDF5 via MPI-IO, etc.) - so running 8 parallel random I/O generating processes on nodes with 28 cores and plenty of RAM (256GB - 512GB) should not be excessive.

I am going to test the latest CentOS kernel next (the one you are referencing).  The RedHat/CentOS kernels are not "old kernel clients" - they contains various backports of hundreds of patches to all kinds of subsystems of Linux.  What is unclear there is exactly what ceph client RedHat is backporting to their kernels. Any pointers there would be helpful.

Andras


On 10/1/18 2:26 PM, Marc Roos wrote:
  How do you test this? I have had no issues under "normal load" with an
old kernel client and a stable os.

CentOS Linux release 7.5.1804 (Core)
Linux c04 3.10.0-862.11.6.el7.x86_64 #1 SMP Tue Aug 14 21:49:04 UTC 2018
x86_64 x86_64 x86_64 GNU/Linux





-----Original Message-----
From: Andras Pataki [mailto:apat...@flatironinstitute.org]
Sent: maandag 1 oktober 2018 20:10
To: ceph-users
Subject: [ceph-users] cephfs kernel client stability

We have so far been using ceph-fuse for mounting cephfs, but the small
file performance of ceph-fuse is often problematic.  We've been testing
the kernel client, and have seen some pretty bad crashes/hangs.

What is the policy on fixes to the kernel client?  Is only the latest
stable kernel updated (4.18.x nowadays), or are fixes backported to LTS
kernels also (like 4.14.x or 4.9.x for example)? I've seen various
threads that certain newer features require pretty new kernels - but I'm
wondering whether newer kernels are also required for better stability -
or - in general, where the kernel client stability stands nowadays.

Here is an example of kernel hang with 4.14.67.  On heavy loads the
machine isn't even pingable.

Sep 29 21:10:16 worker1004 kernel: INFO: rcu_sched self-detected stall
on CPU Sep 29 21:10:16 worker1004 kernel: #0111-...: (1 GPs behind)
idle=bee/140000000000001/0 softirq=21319/21319 fqs=7499 Sep 29 21:10:16
worker1004 kernel: #011 (t=15000 jiffies g=13989 c=13988
q=8334)
Sep 29 21:10:16 worker1004 kernel: NMI backtrace for cpu 1 Sep 29
21:10:16 worker1004 kernel: CPU: 1 PID: 19436 Comm: kworker/1:42
Tainted: P        W  O    4.14.67 #1
Sep 29 21:10:16 worker1004 kernel: Hardware name: Dell Inc. PowerEdge
C6320/082F9M, BIOS 2.6.0 10/27/2017 Sep 29 21:10:16 worker1004 kernel:
Workqueue: ceph-msgr ceph_con_workfn [libceph] Sep 29 21:10:16
worker1004 kernel: Call Trace:
Sep 29 21:10:16 worker1004 kernel: <IRQ> Sep 29 21:10:16 worker1004
kernel: dump_stack+0x46/0x5f Sep 29 21:10:16 worker1004 kernel:
nmi_cpu_backtrace+0xba/0xc0 Sep 29 21:10:16 worker1004 kernel: ?
irq_force_complete_move+0xd0/0xd0 Sep 29 21:10:16 worker1004 kernel:
nmi_trigger_cpumask_backtrace+0x8a/0xc0
Sep 29 21:10:16 worker1004 kernel: rcu_dump_cpu_stacks+0x81/0xb1 Sep 29
21:10:16 worker1004 kernel: rcu_check_callbacks+0x642/0x790 Sep 29
21:10:16 worker1004 kernel: ? update_wall_time+0x26d/0x6e0 Sep 29
21:10:16 worker1004 kernel: update_process_times+0x23/0x50 Sep 29
21:10:16 worker1004 kernel: tick_sched_timer+0x2f/0x60 Sep 29 21:10:16
worker1004 kernel: __hrtimer_run_queues+0xa3/0xf0 Sep 29 21:10:16
worker1004 kernel: hrtimer_interrupt+0x94/0x170 Sep 29 21:10:16
worker1004 kernel: smp_apic_timer_interrupt+0x4c/0x90
Sep 29 21:10:16 worker1004 kernel: apic_timer_interrupt+0x84/0x90 Sep 29
21:10:16 worker1004 kernel: </IRQ> Sep 29 21:10:16 worker1004 kernel:
RIP: 0010:crush_hash32_3+0x1e5/0x270 [libceph] Sep 29 21:10:16
worker1004 kernel: RSP: 0018:ffffc9000fdff5d8 EFLAGS:
00000a97 ORIG_RAX: ffffffffffffff10
Sep 29 21:10:16 worker1004 kernel: RAX: 0000000006962033 RBX:
ffff883f6e7173c0 RCX: 00000000dcdcc373
Sep 29 21:10:16 worker1004 kernel: RDX: 00000000bd5425ca RSI:
000000008a8b0b56 RDI: 00000000b1983b87
Sep 29 21:10:16 worker1004 kernel: RBP: 0000000000000023 R08:
00000000bd5425ca R09: 00000000137904e9
Sep 29 21:10:16 worker1004 kernel: R10: 0000000000000000 R11:
0000000000000002 R12: 00000000b0f29f21
Sep 29 21:10:16 worker1004 kernel: R13: 000000000000000c R14:
00000000f0ae0000 R15: 0000000000000023
Sep 29 21:10:16 worker1004 kernel: crush_bucket_choose+0x2ad/0x340
[libceph] Sep 29 21:10:16 worker1004 kernel:
crush_choose_firstn+0x1b0/0x4c0 [libceph] Sep 29 21:10:16 worker1004
kernel: crush_choose_firstn+0x48d/0x4c0 [libceph] Sep 29 21:10:16
worker1004 kernel: crush_do_rule+0x28c/0x5a0 [libceph] Sep 29 21:10:16
worker1004 kernel: ceph_pg_to_up_acting_osds+0x459/0x850
[libceph]
Sep 29 21:10:16 worker1004 kernel: calc_target+0x213/0x520 [libceph] Sep
29 21:10:16 worker1004 kernel: ? ixgbe_xmit_frame_ring+0x362/0xe80
[ixgbe] Sep 29 21:10:16 worker1004 kernel: ? put_prev_entity+0x27/0x620
Sep 29 21:10:16 worker1004 kernel: ? pick_next_task_fair+0x1c7/0x520 Sep
29 21:10:16 worker1004 kernel:
scan_requests.constprop.55+0x16f/0x280 [libceph] Sep 29 21:10:16
worker1004 kernel: handle_one_map+0x175/0x200 [libceph] Sep 29 21:10:16
worker1004 kernel: ceph_osdc_handle_map+0x390/0x850 [libceph] Sep 29
21:10:16 worker1004 kernel: ? ceph_x_encrypt+0x46/0x70 [libceph] Sep 29
21:10:16 worker1004 kernel: dispatch+0x2ef/0xba0 [libceph] Sep 29
21:10:16 worker1004 kernel: ? read_partial_message+0x215/0x880 [libceph]
Sep 29 21:10:16 worker1004 kernel: ? inet_recvmsg+0x45/0xb0 Sep 29
21:10:16 worker1004 kernel: try_read+0x6f8/0x11b0 [libceph] Sep 29
21:10:16 worker1004 kernel: ? sched_clock_cpu+0xc/0xa0 Sep 29 21:10:16
worker1004 kernel: ? put_prev_entity+0x27/0x620 Sep 29 21:10:16
worker1004 kernel: ? pick_next_task_fair+0x415/0x520 Sep 29 21:10:16
worker1004 kernel: ceph_con_workfn+0x9d/0x5a0 [libceph] Sep 29 21:10:16
worker1004 kernel: process_one_work+0x127/0x290 Sep 29 21:10:16
worker1004 kernel: worker_thread+0x3f/0x3b0 Sep 29 21:10:16 worker1004
kernel: kthread+0xf2/0x130 Sep 29 21:10:16 worker1004 kernel: ?
process_one_work+0x290/0x290 Sep 29 21:10:16 worker1004 kernel: ?
__kthread_parkme+0x90/0x90 Sep 29 21:10:16 worker1004 kernel:
ret_from_fork+0x1f/0x30

Andras

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