Pid wrote:
On 19/12/2011 19:41, Leon Rosenberg wrote:
Do a simple math. If you give each VM up to 384M heap and if you add
some 100 MB for permspace and overhead, you have a consumption of
500MB per VM.
Agreed. Object heap != total process usage.
Take 1GB for OS needs, you have 15, and 15.000/500 makes
it save to run 30 tomcat instances max.
Since you experience the problems after some running time, I would
assume that you VMs are starting with 128 but slowly take up all the
space, and the later VMs just have nothing to get.
Is the OP monitoring the JVM memory consumption (via a JMX connection)?
Advice: Calculate your needs exactly by playing with settings
(remember always set Ms=Mx) and watching gc logs. You will probably
need to reduce the number of instances or buy another machine (or put
more memory into this one).
It would be useful to establish what is consuming memory once Tomcat
instances have failed. Is it failed JVM instances that have hung and
are still consuming memory, or is it something more exotic to do with
the hypervisor?
Fixing memory size will offer some gains, but you need to understand
what each instance is actually doing, rather than using a standard.
Also, do you really need a separate instance for each webapp? You have
60x catalina code in the heap and everything, which probably takes
half of your memory.
I don't think it's safe to say "catalina code will take half your
memory", given that we don't know anything about the OPs apps, but it
may be a reasonable gain to collapse some apps into one Tomcat.
On a 32-bit Linux system, this is what "top" has to say about the memory usage of one
tomcat 5.5 instance, running one single small app, with -Xms128M -Xmx128M, and totally
idle for the time being :
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2871 tomcat55 20 0 539m 137m 4560 S 0.0 9.1 129:40.19 jsvc
If one multiplies this by 60, one gets :
RES : +- 8 GB
VIRT : +- 32 GB
There may be some overhead due to jsvc, but that would be the same under Windows with
tomcat55.exe.
Note also that on a 64-bit system like the OP, the numbers above may be
somewhat larger.
Which make me muse also that since the OP obviously doesn't need a very large heap, he
may benefit, maybe greatly, from running a 32-bit JVM for his Tomcat instances, if that is
allowed under his version of Windows. He may gain even more by running his VM with a
32-bit Windows in the first place.
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