I am using CentOS 7 with "3.10.0-123.4.2.el7.x86_64" version, but I don't know why the kernel threads named
flush aren't present in this kernel version.
I tried to look in the kernel change log, but I didn't find anything.
[root@localhost ~]# ps aux | grep flush [root@localhost ~]# echo $? 1
Without these kernel threads, how are the dirty data flushed?