I'm new to docker. I want to create a docker image for sybase ASE/IQ. And I got some problems these days -- while the DB engine perform IO, there always are much more higher extra IO on the host generated by kworker threads. It impacts the IO performance heavily. I can't find solution for it. Please kind advise. Here's the details --
I'm using a image of sles11 from docker hub -- https://hub.docker.com/r/darksheer/sles11sp4 -- And installed Sybase ASE 15.7 on the container of it. Then while I'm creating the DB server, I found --
1. The srvbuildres command runs very slow -- usually it only takes 3-5 minutes to finish on host, but it takes 1.5h to complete on the docker container.
2. I used "top -d 1" and "iostat -x -k 1" to check IO busy -- found the io_wait is always low , but the svctm are high -- it means the IO is very slow.
3. I use pidstat to trace the IO request on the host , and found -- most IOs were consumed by kworker threads --
Here's a sample while I creating a small test database on docker container --
08:06:05 UID PID kB_rd/s kB_wr/s kB_ccwr/s iodelay Command
08:06:06 1105 66252 0.00 16.00 0.00 0 dataserver
08:06:06 0 66528 0.00 0.00 0.00 1 kworker/2:2
08:06:06 0 66574 0.00 2400.00 0.00 0 kworker/1:0
08:06:06 0 66584 0.00 96.00 0.00 0 kworker/u256:1
08:06:06 UID PID kB_rd/s kB_wr/s kB_ccwr/s iodelay Command
08:06:07 0 65159 0.00 720.00 0.00 0 kworker/u256:7
08:06:07 1105 66252 0.00 112.00 0.00 0 dataserver
08:06:07 0 66528 0.00 11696.00 0.00 2 kworker/2:2
08:06:07 0 66530 0.00 14368.00 0.00 0 kworker/3:1
08:06:07 0 66573 0.00 4768.00 0.00 0 kworker/0:2
08:06:07 0 66574 0.00 4960.00 0.00 1 kworker/1:0
08:06:07 0 66584 0.00 848.00 0.00 0 kworker/u256:1
08:06:07 UID PID kB_rd/s kB_wr/s kB_ccwr/s iodelay Command
08:06:08 0 65159 0.00 2304.00 0.00 0 kworker/u256:7
08:06:08 1105 66252 0.00 208.00 0.00 0 dataserver
08:06:08 0 66528 0.00 18464.00 0.00 0 kworker/2:2
08:06:08 0 66530 0.00 20608.00 0.00 1 kworker/3:1
08:06:08 0 66573 0.00 2256.00 0.00 0 kworker/0:2
08:06:08 0 66574 0.00 18256.00 0.00 0 kworker/1:0
08:06:08 0 66584 0.00 192.00 0.00 0 kworker/u256:1
The IO of kworker is much higher than the DB process -- "dataserver", and made the "create database" completed in 5minutes. And I made a same test on the host out of the container, the pidstat shows --
eisen-suse11:~ # pidstat -d 1
Linux 3.0.101-63-default (eisen-suse11) 01/19/22 _x86_64_
13:30:07 PID kB_rd/s kB_wr/s kB_ccwr/s Command
13:30:08 PID kB_rd/s kB_wr/s kB_ccwr/s Command
13:30:09 PID kB_rd/s kB_wr/s kB_ccwr/s Command
13:30:10 4860 0.00 4.00 0.00 isql
13:30:10 PID kB_rd/s kB_wr/s kB_ccwr/s Command
13:30:11 4845 404.00 404.00 0.00 dataserver
13:30:11 PID kB_rd/s kB_wr/s kB_ccwr/s Command
13:30:12 PID kB_rd/s kB_wr/s kB_ccwr/s Command
So without that kworker, the same "create database" command completed just in 1 seconds... I can't search document for it, only found how to limit the CPU/Memory/GPU resource of kworker-- https://docs.docker.com/config/containers/resource_constraints/ -- But no comments on IO tunning. Please kind help. Thanks in advance for any ideas.
Regards Eisen
Find out the answer -- It's due to the btrfs... Once using ext3/ext4 to contain the DB device file, IO performance is good.