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Re: [rhelv6-list] Limiting pvmove speed with control groups doesn't work as expected



On Tue, Jul 26, 2016 at 4:47 PM, Barry Brimer  wrote:
Maybe ionice could help?


Thanks for your answer Barry, but It would be suboptimal in my opinion for my target that is limiting read overall bandwith....

But I found it !!!

With iotop I see the PID of kcopyd that starts right after pvmove command.... (the kcopyd pid is different every pvmove run, not a fixed process)

[root dbatest1 ~]# ps -ef|grep 11139
root     11139     2  1 17:40 ?        00:00:02 [kcopyd]
root     17103 19305  0 17:43 pts/0    00:00:00 grep 11139

BTW, kcopyd is child of kthreadd:

root         2     0  0 Jun29 ?        00:00:00 [kthreadd]

So I put kcopyd process into the control group too

# echo 11139 > /cgroup/blkio/30M/tasks

so that I now have pvmove process and kcopyd process

[root dbatest1 ~]# cat /cgroup/blkio/30M/tasks
11139
12765

And in fact:

Total DISK READ: 30399.94 K/s | Total DISK WRITE: 30345.65 K/s
  PID  PRIO  USER    DISK READ>  DISK WRITE  SWAPIN      IO    COMMAND                                                                           
11139 be/4 root     29970.89 K/s    0.00 K/s  0.00 %  0.00 % [kcopyd]
12765 be/4 root       65.40 K/s    0.00 K/s  0.00 %  0.91 % pvmove -i 20 /dev/mapper/360a9800037543543~v/mapper/3600a098038303769752b495147377868
36462 be/4 oracle11   20.93 K/s   15.70 K/s  0.00 %  0.08 % ora_ckpt_ALMTEST
 8953 ?dif root        7.85 K/s    0.49 K/s  0.00 %  0.12 % qdiskd
20972 be/4 root        0.00 K/s    0.00 K/s  0.00 %  0.05 % [kjournald]
15733 be/4 root        0.00 K/s    1.31 K/s  0.00 %  0.00 % dsm_om_connsvcd -run
14644 be/4 root        0.00 K/s    1.31 K/s  0.00 %  0.00 % nbdisco
40736 be/4 oracle11    0.00 K/s   15.70 K/s  0.00 %  0.05 % ora_ckpt_TEST
12337 rt/4 root        0.00 K/s    2.62 K/s  0.00 %  0.00 % corosync -f


and

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
sdaq             17.00         7.23         0.00         21          0
sdbf             17.33         7.44         0.00         22          0
sdcy             17.33         7.50         0.00         22          0
sddn             17.33         7.50         0.00         22          0

Thanks anyway ;-)

Gianluca

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