JVM CPU and memory consumption by H2 server

[mansour n]

Hi,

We are testing performance on a Java application which uses a H2 database in server mode (in a dedicated JVM) and we have noticed an important CPU and Heap memory consumption by the H2 JVM even though there is very little or no JDBC activity

For information we monitor H2 JVM with Java Mission Control (via JMX).

In the attached exemple, we have some activity before 14:30 and after 14:30 we have 1.5 req / min (average)

1) Heap Memory

As we can see in screenshot, heap memory is constantly increasing even when we have Major GC, the heap size doesn't return to the initial level. 

The JVM Heap max size is frequently increased from 35Mo to 55Mo.

2) Heap CPU

CPU Heap consumption fluctuates always between 10-20% with some pics over 40% 

We have big constraints in terms of RAM and CPU consumption since we are on an embedded system with a small hardware configuration (1 core and 256 Mo RAM).

Can you tell us how can we optimize this ? limit H2 cache size ? limit H2 background activity

If you have another tools to monitor h2 performance we are also interested for example to get JDBC stats, Cache utilization

JVM args    :  -Xms32M -Xmx64M

JDBC URL : jdbc.h2.url=jdbc:h2:tcp://localhost:1521/k;DB_CLOSE_ON_EXIT=FALSE;TRACE_LEVEL_FILE=4;INIT=CREATE SCHEMA IF NOT EXISTS XXX\\;SET SCHEMA XXX;

H2 version : 1.4.196

Thanks

Mansour

[Noel Grandin]

you'd have to do a deeper investigation to see what exactly is happening and where the memory is going to.


You could try using the older engin (MV_STORE=false) which might have less background activity because it doesn't need
background compaction.