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Oracle Linux: iSCSI Devices Hang on "rq_qos_wait " System Call (Doc ID 2769797.1)

Last updated on AUGUST 26, 2021

Applies to:

Oracle Cloud Infrastructure - Version N/A and later
Linux OS - Version Oracle Linux 7.0 and later
Information in this document applies to any platform.


Under heavy IO, iSCSI block volumes hang.

Checking the system call stack of the hang processes they frequently stay in "rq_qos_wait"

$ sudo  ps -eo pid,stat,wchan:30,comm | grep D 
   PID STAT WCHAN                          COMMAND 
  2570 D    wait_on_page_bit               dd 
  5514 D    rq_qos_wait                    kworker/u64:1+f 
  7115 D+   xfs_ilock                      ls 
 12596 D+   xfs_ilock                      ls 
 14067 D+   rq_qos_wait                    vim 
 16030 D    rq_qos_wait                    kworker/0:1+xfs 
 16982 D    xfs_ilock                      ls 
 22192 D+   balance_dirty_pages            dd 
 25037 D    rwsem_down_write_slowpath      xfs_io 
 25269 D    xfs_ilock                      ls 
 26291 D    rq_qos_wait                    dd 
 26602 D    rwsem_down_write_slowpath      chmod 
 27215 D    rwsem_down_write_slowpath      xfs_io 
 29329 D    wb_wait_for_completion         sync 
 29999 D    rq_qos_wait                    dd 
 31573 D+   rq_qos_wait                    dd




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