On Thu, Jul 26, 2018 at 9:49 AM, Ilya Dryomov <idryomov@xxxxxxxxx> wrote: > On Thu, Jul 26, 2018 at 1:07 AM Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx> wrote: >> >> On Wed, Jul 25, 2018 at 6:07 PM, Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx> wrote: >> > On Wed, Jul 25, 2018 at 5:51 PM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote: >> >> >> >> >> >> On Wed, Jul 25, 2018 at 5:41 PM Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx> >> >> wrote: >> >>> >> >>> I am not sure this related to RBD, but in case it is, this would be an >> >>> important bug to fix. >> >>> >> >>> Running LVM on top of RBD, XFS filesystem on top of that, consumed in RHEL >> >>> 7.4. >> >>> >> >>> When running a large read operation and doing LVM snapshots during >> >>> that operation, the block being read winds up all zeroes in pagecache. >> >>> >> >>> Dropping the caches syncs up the block with what's on "disk" and >> >>> everything is fine. >> >>> >> >>> Working on steps to reproduce simply - ceph is Luminous 12.2.7, RHEL >> >>> client is Jewel 10.2.10-17.el7cp >> >> >> >> >> >> Is this krbd or QEMU+librbd? If the former, what kernel version are you >> >> running? >> > >> > It's krbd on RHEL. >> > >> > RHEL kernel: >> > >> > Linux dmg-cbcache01 3.10.0-862.el7.x86_64 #1 SMP Wed Mar 21 18:14:51 >> > EDT 2018 x86_64 x86_64 x86_64 GNU/Linux >> >> Not sure if this is exactly replicating the issue, but I was able to >> do this on two different systems: >> >> RHEL 7.4 kernel as above. > > 3.10.0-862.el7 is a RHEL 7.5 kernel. > I think you have a 7.4 system with a 7.5 kernel. > >> >> Create a PVM PV on a mapped kRBD device >> >> example: pvcreate /dev/rbd/spin1/lvm1 >> >> Create a VG and LV, make an XFS FS >> >> vgcreate datavg /dev/rbd/spin1/lvm1 >> lvcreate -n data1 -L 5G datavg >> mkfs.xfs /dev/datavg/data1 >> <mount on something> >> >> Get some large file and copy it to some other file, same storage or >> different. All is well. > > Same storage as in the same XFS filesystem? Is copying it from > /mnt/foo to /mnt/bar enough (assuming /dev/datavg/data1 is on /mnt)? > >> >> Now snapshot the LV >> >> lvcreate -l8%ORIGIN -s -n snap_data1 /dev/datavg/data1 --addtag backup > > 8% of 5G is 400M. How large is the file? > >> >> Now try to copy that file again. I get: >> >> NMI watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [kworker/2:1:3470] >> >> And in dmesg (this is on Proxmox but I did the same on ESXi) >> >> [1397609.308673] sched: RT throttling activated >> [1397658.759259] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 23s! >> [kworker/0:1:2648] >> [1397658.759354] Modules linked in: dm_snapshot dm_bufio rbd libceph >> rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace fscache >> sunrpc ppdev joydev pcspkr sg parport_pc virtio_balloon parport shpchp >> i2c_piix4 ip_tables xfs libcrc32c sd_mod sr_mod crc_t10dif >> crct10dif_generic cdrom crct10dif_common ata_generic pata_acpi >> virtio_scsi virtio_console virtio_net bochs_drm drm_kms_helper >> syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm ata_piix libata >> serio_raw virtio_pci i2c_core virtio_ring virtio floppy dm_mirror >> dm_region_hash dm_log dm_mod >> [1397658.759400] CPU: 0 PID: 2648 Comm: kworker/0:1 Kdump: loaded Not >> tainted 3.10.0-862.el7.x86_64 #1 >> [1397658.759402] Hardware name: QEMU Standard PC (i440FX + PIIX, >> 1996), BIOS rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org >> 04/01/2014 >> [1397658.759415] Workqueue: kcopyd do_work [dm_mod] >> [1397658.759418] task: ffff932df65d3f40 ti: ffff932fb138c000 task.ti: >> ffff932fb138c000 >> [1397658.759420] RIP: 0010:[<ffffffffc08535a0>] [<ffffffffc08535a0>] >> copy_callback+0x50/0x130 [dm_snapshot] >> [1397658.759426] RSP: 0018:ffff932fb138fd08 EFLAGS: 00000283 >> [1397658.759428] RAX: 000000000003e5e8 RBX: ffffebecc4943ec0 RCX: >> ffff932ff4704068 >> [1397658.759430] RDX: ffff932dc8050d00 RSI: ffff932fd6a0f9b8 RDI: >> 0000000000000000 >> [1397658.759431] RBP: ffff932fb138fd28 R08: ffff932dc7d2c0b0 R09: >> ffff932dc8050d20 >> [1397658.759433] R10: 00000000c7d2b301 R11: ffffebecc01f4a00 R12: >> 0000000000000000 >> [1397658.759435] R13: 0000000180090003 R14: 0000000000000000 R15: >> 00000000ffffff80 >> [1397658.759438] FS: 0000000000000000(0000) GS:ffff932fffc00000(0000) >> knlGS:0000000000000000 >> [1397658.759440] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >> [1397658.759442] CR2: 00007f17bcd5e860 CR3: 0000000042c0e000 CR4: >> 00000000000006f0 >> [1397658.759447] Call Trace: >> [1397658.759452] [<ffffffffc0853550>] ? origin_resume+0x70/0x70 [dm_snapshot] >> [1397658.759459] [<ffffffffc0340eab>] run_complete_job+0x6b/0xc0 [dm_mod] >> [1397658.759466] [<ffffffffc0340f60>] process_jobs+0x60/0x100 [dm_mod] >> [1397658.759471] [<ffffffffc0340e40>] ? kcopyd_put_pages+0x50/0x50 [dm_mod] >> [1397658.759477] [<ffffffffc0341042>] do_work+0x42/0x90 [dm_mod] >> [1397658.759483] [<ffffffffa08b2dff>] process_one_work+0x17f/0x440 >> [1397658.759485] [<ffffffffa08b3bcc>] worker_thread+0x22c/0x3c0 >> [1397658.759489] [<ffffffffa08b39a0>] ? manage_workers.isra.24+0x2a0/0x2a0 >> [1397658.759494] [<ffffffffa08bae31>] kthread+0xd1/0xe0 >> [1397658.759497] [<ffffffffa08bad60>] ? insert_kthread_work+0x40/0x40 >> [1397658.759503] [<ffffffffa0f1f637>] ret_from_fork_nospec_begin+0x21/0x21 >> [1397658.759506] [<ffffffffa08bad60>] ? insert_kthread_work+0x40/0x40 > > Did you experiment with the snapshot chunk size (lvcreate --chunksize)? > I wonder if the default shapshot chunk size is the same on RHEL 7.4 and > Ubuntu you tried 4.14.39 on. > > Thanks, I also asked the database people what type of IO is being done when they got the zeroes in page cache vs. good data on "disk:, here is the response: Normal user process will open a database file using O_RDONLY, and will read data from it with pread in 8192 byte sized requests Thank you, Alex _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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