[DRBD-user] umount /drbdpart takes >50 seconds

[Lars Ellenberg]

On Wed, Dec 12, 2018 at 10:16:09AM +0100, Harald Dunkel wrote:
> Hi folks,
> 
> using drbd umounting /data1 takes >50 seconds, even though the file
> system (ext4, noatime, default) wasn't accessed for more than 2h.
> umount ran with 100% CPU load.
> 
> # sync
> # time umount /data1
> 
> real    0m52.772s
> user    0m0.000s
> sys     0m52.740s
> 
> 
> This appears to be a pretty long time. I am concerned that there
> is some data sleeping in a buffer that gets flushed only at umount
> time.
> 
> Kernel is version 4.18.0-0.bpo.1-amd64 on Debian Stretch. drbdutils
> is 8.9.10-2. drbd.conf is attached. The bond2 interface used for
> drbd synchronization is based upon 2 * 10 Gbit/sec NICs.
> 
> Every insightful comment is highly appreciated.

Unlikely to have anything to do with DRBD.

since you apparently can reproduce, monitor
grep -e Dirty -e Writeback /proc/meminfo
and slabtop before/during/after umount.

Also check sysctl settings
sysctl vm | grep dirty

-- 
: Lars Ellenberg
: LINBIT | Keeping the Digital World Running
: DRBD -- Heartbeat -- Corosync -- Pacemaker

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