On 2/24/2015 10:16 AM, Christopher Schultz wrote:
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Daniel,
On 2/24/15 8:01 AM, Daniel Mikusa wrote:
On Tue, Feb 24, 2015 at 7:33 AM, Peter Irbizon
<peterirbi...@gmail.com> wrote:
Hello, I would like to know if it is normal that tomcat7 runs on
3.9% CPU when idle? I saw all other processes are at 0%, only
tomcat7 is always at least 3.9%.
1.) What's your system like? How many CPUs / cores? Is it a VM or
hardware? What is the specific version of Tomcat? of Java? What
OS are you running?
2.) How are you determining it's idle? As John mention, do you
have any apps deployed? Do you know if traffic is hitting the
server?
3.) Can you run a profiler and attach it to Tomcat? It'll tell
you what's happening inside the JVM.
4. Take a few thread dumps to see what the JVM threads are doing.
When truly idle (i.e. no requests are being processed), Tomcat runs a
maintenance thread that performs some background tasks, but that runs
about once every 60 seconds and does very little, depending on what
you have configured.
So unless you are seeing that thread specifically running at its
interval, Tomcat's threads are totally blocked waiting on various
events to occur (like an I/O event for an incoming request, or waiting
for a timeout to perform that maintenance).
On a dev server, I just checked and my Tomcat processes go down to 0.0
CPU as measured by top when they aren't "doing" anything.
There is also the question of "3.9% of what"? If it's a slow, single
core machine, it's a lot more likely that TC might use 3% of it, than it
is if it's a 16-core 3.5GHz server.
The thread dumps will likely tell the story.
- -chris
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