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High CPU
https://forum.linode.com/viewtopic.php?f=19&t=11417		 Page 1 of 1
Author:  sneakyfitch [ Thu Nov 13, 2014 2:17 pm ]
Post subject:  High CPU
I am trying to determine the source of and find a remedy to consistently high CPU use in my VPS. By high, I mean 90% and above.

When I less /var/log/messages I see the majority of the messages are Firewall: *TCP_IN Blocked* messages. Is this the source of my problem, or should I be looking deeper?
Author:  akerl [ Thu Nov 13, 2014 2:22 pm ]
Post subject:  Re: High CPU
Have you considered checking what is using your CPU?
Author:  sneakyfitch [ Thu Nov 13, 2014 4:09 pm ]
Post subject:  Re: High CPU
akerl wrote:
Have you considered checking what is using your CPU?


Actually, I did and I should have mentioned that. However, while I understand some of the things going on I don't understand everything. I'm not a sysadmin by training and only in practice when I have to be.

As I look at top I don't see anything that jumps out at me as a problem. The sites being hosted are low traffic sites, so I don't expect to see and am not seeing a lot of activity from MySQL and PHP.

Code:
 mysql     20   0 1192m 416m 6276 S    2 27.6   1423:56 mysqld
    7 root      20   0     0    0    0 S    0  0.0   1762:16 rcu_sched
16486 root      20   0  4796 2540 2364 S    0  0.2   0:00.09 bash
17345 root      20   0  2532 1980 1656 R    0  0.1   0:00.09 top
    1 root      20   0  2080   76    0 S    0  0.0   9:26.50 init
    2 root      20   0     0    0    0 S    0  0.0   0:00.17 kthreadd
    3 root      20   0     0    0    0 S    0  0.0  90:08.32 ksoftirqd/0
    4 root      20   0     0    0    0 S    0  0.0   0:00.06 kworker/0:0
    5 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/0:0H
    8 root      20   0     0    0    0 S    0  0.0   0:00.00 rcu_bh
    9 root      RT   0     0    0    0 S    0  0.0  13:16.63 migration/0
   10 root      RT   0     0    0    0 S    0  0.0  11:08.58 migration/1
   11 root      20   0     0    0    0 S    0  0.0  93:30.14 ksoftirqd/1
   12 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/1:0
   13 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/1:0H
   14 root      RT   0     0    0    0 S    0  0.0  10:58.86 migration/2
   15 root      20   0     0    0    0 S    0  0.0  93:46.01 ksoftirqd/2
   16 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/2:0
   17 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/2:0H
   18 root      RT   0     0    0    0 S    0  0.0  11:12.97 migration/3
   19 root      20   0     0    0    0 S    0  0.0  93:25.68 ksoftirqd/3
   20 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/3:0
   21 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/3:0H
   22 root      RT   0     0    0    0 S    0  0.0  11:56.06 migration/4
   23 root      20   0     0    0    0 S    0  0.0  89:39.02 ksoftirqd/4
   24 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/4:0
   25 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/4:0H
   26 root      RT   0     0    0    0 S    0  0.0  12:16.67 migration/5
   27 root      20   0     0    0    0 S    0  0.0  93:40.16 ksoftirqd/5
   28 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/5:0
   29 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/5:0H
Author:  akerl [ Thu Nov 13, 2014 4:13 pm ]
Post subject:  Re: High CPU
That would probably be saner to read if you'd left the headers, but it looks like MySQL is what's using the most CPU.
Author:  sneakyfitch [ Thu Nov 13, 2014 4:21 pm ]
Post subject:  Re: High CPU
sneakyfitch wrote:
...while I understand some of the things going on I don't understand everything. I'm not a sysadmin by training and only in practice when I have to be.


I read where elsewhere that something to look at was to run echo l > /proc/sysrq-trigger and then see what it reports by using dmesg.

Doing that I get a lot of the same things I saw before. There are lots of Firewall: *TCP_IN Blocked* and an occasional Firewall: *UDP_IN Blocked* and Firewall: *Port Flood*.

At the end of that report I see this, but I don't know what it means of it it has any significance at all:

Quote:
SysRq : Show backtrace of all active CPUs
sending NMI to all CPUs:
xen: vector 0x2 is not implemented
SysRq : Show backtrace of all active CPUs
sending NMI to all CPUs:
xen: vector 0x2 is not implemented
Author:  akerl [ Thu Nov 13, 2014 4:24 pm ]
Post subject:  Re: High CPU
I have no idea why you're looking around at your firewall logs or sysrqs.

Any utility like top or htop will show you what is using CPU. Based on what you pasted above, it's MySQL.

Figure out what's happening when your usage spikes, and then figure out how to make that not use as much CPU.

- Les
Author:  sneakyfitch [ Thu Nov 13, 2014 4:30 pm ]
Post subject:  Re: High CPU
akerl wrote:
That would probably be saner to read if you'd left the headers, but it looks like MySQL is what's using the most CPU.


Sorry. You are correct. I don't know why it didn't copy.

Code:
aegir:~# top
top - 15:24:42 up 101 days, 16:29,  1 user,  load average: 1.14, 1.19, 1.34
Tasks: 168 total,   3 running, 165 sleeping,   0 stopped,   0 zombie
Cpu(s): 16.1%us,  2.8%sy,  0.0%ni, 80.6%id,  0.0%wa,  0.0%hi,  0.0%si,  0.5%st
Mem:   1546224k total,  1435604k used,   110620k free,    35932k buffers
Swap:   262140k total,        0k used,   262140k free,   698112k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
32435 smithbas  20   0 68176  42m  18m R   35  2.8   0:01.06 php
32460 smithbas  20   0 62420  36m  18m R   15  2.4   0:00.46 php
    7 root      20   0     0    0    0 S    0  0.0   1762:34 rcu_sched
28148 root      20   0  2532 1976 1656 R    0  0.1   0:00.41 top
31290 root      20   0  4824 2544 2348 S    0  0.2   0:00.03 bash
    1 root      20   0  2080   76    0 S    0  0.0   9:26.59 init
    2 root      20   0     0    0    0 S    0  0.0   0:00.17 kthreadd
    3 root      20   0     0    0    0 S    0  0.0  90:09.04 ksoftirqd/0
    4 root      20   0     0    0    0 S    0  0.0   0:00.06 kworker/0:0
    5 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/0:0H
    8 root      20   0     0    0    0 S    0  0.0   0:00.00 rcu_bh
    9 root      RT   0     0    0    0 S    0  0.0  13:16.71 migration/0
   10 root      RT   0     0    0    0 S    0  0.0  11:26.89 migration/1
   11 root      20   0     0    0    0 S    0  0.0  93:30.78 ksoftirqd/1
   12 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/1:0
   13 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/1:0H
   14 root      RT   0     0    0    0 S    0  0.0  11:12.72 migration/2
   15 root      20   0     0    0    0 S    0  0.0  93:46.97 ksoftirqd/2
   16 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/2:0
   17 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/2:0H
   18 root      RT   0     0    0    0 S    0  0.0  11:13.05 migration/3
   19 root      20   0     0    0    0 S    0  0.0  93:26.51 ksoftirqd/3
   20 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/3:0
   21 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/3:0H
   22 root      RT   0     0    0    0 S    0  0.0  12:02.22 migration/4
   23 root      20   0     0    0    0 S    0  0.0  89:39.61 ksoftirqd/4
   24 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/4:0
   25 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/4:0H
   26 root      RT   0     0    0    0 S    0  0.0  12:19.94 migration/5
   27 root      20   0     0    0    0 S    0  0.0  93:40.97 ksoftirqd/5
   28 root      20   0     0    0    0 S    0  0.0   0:00.00 kworker/5:0
   29 root       0 -20     0    0    0 S    0  0.0   0:00.00 kworker/5:0H
   30 root      RT   0     0    0    0 S    0  0.0  12:06.26 migration/6
Author:  sneakyfitch [ Thu Nov 13, 2014 4:40 pm ]
Post subject:  Re: High CPU
When I look at Longview from the Linode Manager I see almost a flat line at around 100% in the CPU graph. "User" appears to be the primary consumer.

That may or may not be helpful, but this is where I start to run short on understanding what's going on.
Author:  akerl [ Thu Nov 13, 2014 4:45 pm ]
Post subject:  Re: High CPU
Go look at the processes section to see which processes that refers to
Author:  sneakyfitch [ Thu Nov 13, 2014 5:07 pm ]
Post subject:  Re: High CPU
akerl wrote:
Go look at the processes section to see which processes that refers to


If you mean look at the Process Explorer section of Longview, nothing jumps out at me there. The highest CPU consumer is mysqld at just 2%.
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