DIRECT and ASYNC I/O operations on mdraid generates lots of kworker processes and causes performance issues
Issue
-
The Oracle DB is configured to use a filesystem created over lvm volume. This
LV
is created on top of RAID 10mdraid
device set up usingnvme
disks. As soon as the Oracle DB startsDIRECT
andASYNC
IO operations, there are large number ofkworker
processes created and system load average increases significantly. This also results in a severe IO performance issue.-
Oracle parameter
filesystemio_options=SETALL
also causes similar issue, since this option in DB would allow it to useDIRECT
andASYNC
IO operations on above filesystem, lvm volume created onmdraid
. -
In some occurrences these
kworker
processes will keep hogging CPU usage for about 30 minutes even though there's no more running workload.
-
Environment
- Red Hat Enterprise Linux 7.4
kernel: 3.10.0-693.25.4.el7
EXT4
/XFS
filesystem created on lvm volume usingmdraid
as aPV
.mdraid
withRAID 10
set up created usingnvme
disks- Oracle database configured to use
DIRECT
andASYNC
IO
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