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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: High load from tomcat, no users, no errors
Date Fri, 06 Jul 2012 17:56:44 GMT
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Francis,

On 7/6/12 12:52 PM, francis picabia wrote:
> I have two servers with Debian 6 and an older tomcat 5.0.30

Echoing Chuck's comments: upgrade. You are almost 4 major releases behind.

> top - 13:41:38 up 30 days,  6:21,  2 users,  load average: 0.00,
> 0.00, 0.00

Load average: 0.00 0.00 0.00

High load?

Note that your OS may or may not count individual threads as processes
for the purposes of computing the load average (which, on Linux, is
the average length of the run queue in number-of-processes). If your
kernel doesn't count threads separately, then you can have an
effective load of, say, 100, even though your load average only says
1.00 (because it's all counted as one process). Just be sure you know
what your numbers mean.

> Tasks: 263 total,   2 running, 261 sleeping,   0 stopped,   0
> zombie Cpu(s):  4.7%us,  4.4%sy,  0.0%ni, 90.3%id,  0.0%wa,
> 0.0%hi,  0.5%si,  0.0%st Mem:  16461112k total, 16335376k used,
> 125736k free,   549972k buffers Swap:  3906552k total,        0k
> used,  3906552k free, 14871648k cached

CPU(s) is(are) 90% idle. High load? Looks like even user/system use
which suggests that at least something is being accomplished.

> PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND 
> 23648 tomcat    20   0 4623m 203m  10m S  109  1.3 284:04.69 java

109% of your CPU suggests that more than one CPU is in use: how many
do you have?

> I should add that the tomcat apps all appear to work, but we are 
> simply seeing a very high load.

You mean lots of apparent CPU usage.

> "TP-Processor1" daemon prio=10 tid=0x00007f18342f2000 nid=0x5c8e 
> runnable [0x00007f18338f7000] java.lang.Thread.State: RUNNABLE at
> java.net.SocketInputStream.socketRead0(Native Method) at
> java.net.SocketInputStream.read(SocketInputStream.java:129) at
> java.io.BufferedInputStream.fill(BufferedInputStream.java:218) at
> java.io.BufferedInputStream.read1(BufferedInputStream.java:258) at
> java.io.BufferedInputStream.read(BufferedInputStream.java:317) -
> locked <0x00000007ac54b6c0> (a java.io.BufferedInputStream) at
> org.apache.jk.common.ChannelSocket.read(ChannelSocket.java:598) at
> org.apache.jk.common.ChannelSocket.receive(ChannelSocket.java:535) 
> at
> org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:663)
>
> 
at org.apache.jk.common.SocketConnection.runIt(ChannelSocket.java:866)
> at
> org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
>
> 
at java.lang.Thread.run(Thread.java:662)

This thread is handling a request: are you sure there is no traffic?

All other threads are idle or blocked on some condition, which means
they shouldn't be using any CPU at all.

Are you sure you got a thread dump from the right process?

- -chris
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