Most of us know these
commands or arguments. Still wanted to collect and have it in Single place.
Check
a java process status
ps –ef | grep java or
jps
Check
java application status by specifying application status
jps –lv | grep <app
name>
Example jps –lv | grep
managed
To
know about java process information including arguments
jinfo <PID>
<-d64>
-d64 is required when
java process is running on 64 platform
To
get stack trace or thread dumps
jstack < PID >
It can be redirected to
an output file
To
get heap dump for memory issue analysis
jmap
-dump:live,format=b,file=heap.bin <pid>
Generating a heap in
production environment is not recommended. So can capture only historical data
using,
jmap -histo:live <pid> >> filename.txt
To
understand what each thread is doing at the time of a crash
Jdb
ptree – to known the
process tree- can view parent processes
Useful Java parameters
Some
options may vary per architecture/OS/JVM version. Boolean options are turned on
with -XX:+<option> and turned off with -XX:-<option>.
Numeric options are set with -XX:<option>=<number>. Numbers
can include 'm' or 'M' for megabytes, 'k' or 'K' for kilobytes, and 'g' or 'G'
for gigabytes (for example, 32k is the same as 32768). String options are set
with -XX:<option>=<string>, are usually used to specify a
file, a path, or a list of commands
Set
Heap Size
Xms<size>, Xmx<size>,
Sizing
Young Generation
Xmn<size>
XX:MaxNewSize=size
PermSpace
sizing
-XX:MaxPermSize=64m
Size
Thread Stack size
-XX:ThreadStackSize=512
Print
GC details
-Xloggc:<filename> Log GC verbose output to specified
file. The verbose output is controlled by the normal verbose GC flags.
-XX:-UseGCLogFileRotation Enabled GC log rotation, requires
-Xloggc.
-XX:NumberOfGClogFiles=1
-XX:GCLogFileSize=8K
-XX:-PrintGC Print messages at garbage collection.
Manageable.
-XX:-PrintGCDetails Print more details at garbage
collection. Manageable. (Introduced in 1.4.0.)
-XX:-PrintGCTimeStamps Print timestamps
GC
algorithm
Parallel
GC- New and old generation
XX:+UseParallelGC,X:+UseParallelOldGC,XX:ParallelGCThreads=24
G1
GC
-XX:+UseG1GC
-XX:G1ReservePercent=n -XX:G1HeapRegionSize=n
Concurrent
GC –Old Generation
-XX:-UseConcMarkSweepGC
-XX:ConcGCThreads=n
Disable Explicit
Garbage collection
-XX:-DisableExplicitGC
