On 3/10/16 2:33 PM, Christopher Schultz wrote:
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Rallavagu,
On 3/10/16 5:16 PM, Rallavagu wrote:
On 3/10/16 2:09 PM, Christopher Schultz wrote: Rallavagu,
On 3/10/16 4:02 PM, Rallavagu wrote:
On 3/10/16 11:54 AM, Christopher Schultz wrote:
Are you sure you have matched-up the correct thread within
the JVM that is using all that CPU?
How are you measuring the CPU usage?
It would the ID output from "top -H" mapping to "Native ID"
in thread dump.
My version of 'top' (Debian Linux) doesn't show thread ids. :(
I seem to recall having to do some backflips to convert native
thread id to Java thread id. Can you explain what you've done to do
that?
A typical top -H shows the following
top - 11:40:11 up 190 days, 1:24, 1 user, load average: 5.74,
6.09, 5.78 Tasks: 759 total, 4 running, 755 sleeping, 0
stopped, 0 zombie Cpu(s): 18.4%us, 1.6%sy, 0.0%ni, 79.5%id,
0.1%wa, 0.0%hi, 0.5%si, 0.0%st Mem: 8057664k total, 7895252k
used, 162412k free, 63312k buffers Swap: 2064380k total,
199452k used, 1864928k free, 2125868k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
COMMAND 15648 tomcat 20 0 9649m 4.8g 4520 R 87.3 62.6
7:24.24 java 21710 tomcat 20 0 9649m 4.8g 4520 R 79.8 62.6
5:44.99 java 21694 tomcat 20 0 9649m 4.8g 4520 S 74.3 62.6
5:39.40 java 7889 tomcat 20 0 9649m 4.8g 4520 S 29.7 62.6
4:24.44 java 7878 tomcat 20 0 9649m 4.8g 4520 S 27.8 62.6
4:36.82 java 21701 tomcat 20 0 9649m 4.8g 4520 S 26.0 62.6
5:49.83 java
After taking thread dump, I used Threadlogic which will show
Native-ID as column which corresponds to PID shown above.
https://java.net/projects/threadlogic
This way it helps to determine the thread that might potentially
causing high cpu.
Okay. Are you serving a high rate of requests? It's possible that the
thread is just doing a lot of (legitimate) work.
The BIO connector is very basic: it uses blocking reads, and the
thread dump you showed before showed it waiting on IO, so it should be
completely idle, using no CPU time.
It's *possible* that it's in a busy-wait state where it is performing
a very short IO-wait in a loop that it never exits. But since you
haven't specified any weird timeouts, etc. on your connector, I'm
skeptical as to that being the cause.
This thread stays at high CPU usage for quite a while? And every
thread dump you do has the same (or very similar) stack trace?
The symptom is that app is always high on CPU hovering between 75 - 85
and so looked at the thread dumps. Each thread dump shows few high cpu
threads and some of those are supposedly idle. After looking at a
particular thread by Id what it was doing in the previous thread some of
these were reading on socket. So, that might be somewhat related to what
you said about I/O wait.
Also, if BIO is basic, what are other options?
Thanks
- -chris
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