How to check heap usage of a running JVM from the command line

Question

Can I check heap usage of a running JVM from the commandline  I mean the actual usage rather than the max amount allocated with Xmx   I need it to be commandline because I don t have access to a windowing environment  and I want script based on the value   the application is running in Jetty Application server

User · Answer

If you start execution with gc logging turned on you get the info on file. Otherwise 'jmap -heap ' will give you what you want. See the jmap doc page for more.

Please note that jmap should not be used in a production environment unless absolutely needed as the tool halts the application to be able to determine actual heap usage. Usually this is not desired in a production environment.

User · Answer

For Java 8 you can use the following command line to get the heap space utilization in kB   jstat -gc  lt PID gt    tail -n 1   awk   split  0 a       sum a 3  a 4  a 6  a 8   print sum     The command basically sums up    S0U  Survivor space 0 utilization  kB   S1U  Survivor space 1 utilization  kB   EU  Eden space utilization  kB   OU  Old space utilization  kB     You may also want to include the metaspace and the compressed class space utilization  In this case you have to add a 10  and a 12  to the awk sum

User · Answer

All procedure at once  Based on  Till Sch  fer answer  In KB    jstat -gc   ps axf   egrep -i  quot   bin java   quot    egrep -v grep   awk   print  1      tail -n 1   awk   split  0 a  quot   quot    sum  a 3  a 4  a 6  a 8  a 10    printf  quot   2f KB n quot  sum     In MB    jstat -gc   ps axf   egrep -i  quot   bin java   quot    egrep -v grep   awk   print  1      tail -n 1   awk   split  0 a  quot   quot    sum  a 3  a 4  a 6  a 8  a 10   1024  printf  quot   2f MB n quot  sum      quot Awk sum quot  reference   a 1  - S0C  a 2  - S1C  a 3  - S0U  a 4  - S1U  a 5  - EC  a 6  - EU  a 7  - OC  a 8  - OU  a 9  - PC a 10  - PU a 11  - YGC a 12  - YGCT a 13  - FGC a 14  - FGCT a 15  - GCT  Used for  quot Awk sum quot   a 3  --  S0U  Survivor space 0 utilization  KB   a 4  --  S1U  Survivor space 1 utilization  KB   a 6  --  EU  Eden space utilization  KB   a 8  --  OU  Old space utilization  KB   a 10  -  PU  Permanent space utilization  KB     Ref   https   docs oracle com javase 7 docs technotes tools share jstat html   Thanks  NOTE  Works to OpenJDK  FURTHER QUESTION  Wrong information  If you check memory usage with the ps command  you will see that the java process consumes much more    ps -eo size pid user command --sort -size   egrep -i  quot   bin java   quot    egrep -v grep   awk    hr  1 1024   printf  quot   2f MB  quot  hr      for   x 4   x lt  NF   x       printf  quot  s  quot   x    print  quot  quot       cut -d  quot  quot  -f2   cut -d  quot - quot  -f1   UPDATE  2021-02-16   According to the reference below  and  Till Sch  fer comment   quot ps can show total reserved memory from OS quot   adapted  and  quot jstat can show used space of heap and stack quot   adapted   So  we see a difference between what is pointed out by the ps command and the jstat command  According to our understanding  the most  quot realistic quot  information would be the ps output since we will have an effective response of how much of the system s memory is compromised  The command jstat serves for a more detailed analysis regarding the java performance in the consumption of reserved memory from OS   Ref   http   www openkb info 2014 06 how-to-check-java-memory-usage html

User · Answer

You can use jstat  like      jstat -gc pid   Full docs here    http   docs oracle com javase 7 docs technotes tools share jstat html

[java] How to check heap usage of a running JVM from the command line?

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