[ceph-users] cephfs kernel client stability

Andras Pataki apataki at flatironinstitute.org
Mon Oct 1 12:02:44 PDT 2018


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:apataki at 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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