How to easily decrease the heap size for your server product?

-

 Hi, community! 

 

I would like to share my experience using the String deduplication functionality in JVM. 

A suggestion was based on community questions and GC logs provided by members, where I have not seen that feature on JVM parameters. 

Disclaimer,  as usual, everything should be tested in the test-environment first.

My use case was started from the next situation, if you have a system where you can not extend RAM easier and don't want to use as a swap file.  

Well let's start, as you know that a string deduplication feature added into Java 8 update 20 (it is super old release, 2014).

All technical info you can in JEP-192 - http://openjdk.java.net/jeps/192

 

You can enabled in G1 GC with next parameters:

-XX:+UseG1GC -XX:+UseStringDeduplication -XX:+PrintStringDeduplicationStatistics

 

  • UseStringDeduplication (bool) -  Enable string deduplication

  • PrintStringDeduplicationStatistics (bool) - Print detailed deduplication statistics

  • StringDeduplicationAgeThreshold (uintx) - String objects reaching this age will be considered candidates for deduplication

 

Let's see the results on monitoring:

image.png

The yellow line is non-heap memory usage, the green is heap memory. 

In this case, I especially removed the value of GB. Because that optimisation is really individual for every instance. Because we are using 3rd-party plugins and own apps. Where all those parameters reflected to value and also, some plugins (apps) starting to be better after implementing the DC compatibility requirements. (Thanks for that Atlassian). 

But the  last statistics you can read in this stats output, reading that info I decreased in our 3rd party app a String usage.

2019-03-03T22:32:49.221+0100: 843349.318: [GC concurrent-string-deduplication, 15.6M->82.4K(15.5M), avg 78.5%, 0.1523212 secs]
[Last Exec: 0.1523212 secs, Idle: 11.6095757 secs, Blocked: 2/0.0201580 secs]
[Inspected: 184339]
[Skipped: 0( 0.0%)]
[Hashed: 136198( 73.9%)]
[Known: 30( 0.0%)]
[New: 184309(100.0%) 15.6M]
[Deduplicated: 182894( 99.2%) 15.5M( 99.5%)]
[Young: 182894(100.0%) 15.5M(100.0%)]
[Old: 0( 0.0%) 0.0B( 0.0%)]
[Total Exec: 22129/365.6814278 secs, Idle: 22129/842910.6783849 secs, Blocked: 14649/68.0063332 secs]
[Inspected: 434930188]
[Skipped: 2( 0.0%)]
[Hashed: 270134906( 62.1%)]
[Known: 2133448( 0.5%)]
[New: 432796738( 99.5%) 27.6G]
[Deduplicated: 405747212( 93.8%) 21.6G( 78.5%)]
[Young: 213685766( 52.7%) 12.4G( 57.5%)]
[Old: 192061446( 47.3%) 9423.7M( 42.5%)]
[Table]
[Memory Usage: 258.9M]
[Size: 8388608, Min: 1024, Max: 16777216]
[Entries: 8146001, Load: 97.1%, Cached: 371239, Added: 28627150, Removed: 20481149]
[Resize Count: 13, Shrink Threshold: 5592405(66.7%), Grow Threshold: 16777216(200.0%)]
[Rehash Count: 0, Rehash Threshold: 120, Hash Seed: 0x0]
[Age Threshold: 3]
[Queue]
[Dropped: 0]
[GC concurrent-string-deduplication, deleted 1 entries, 0.0000053 secs]

Well, I hope you have concerns related to time for execute that functionality:

image.png

Where we can see that function works often. but it is interesting how much need to complete 1 time review string deduplication.

image.png  

As you see it fastest phase of G1 GC.

Let's see the situation of with CPU, because we need to pay to CPU :).

Снимок экрана 2019-03-04 в 1.11.08.png

 

 

image.png

In my situation, everything is ok. Also, I see my CPU is wasting time ;)

Conclusion:

If you want to balance CPU and RAM usage for your JVM, by string deduplication feel free to use it. Because it is an easy to win.  

I hope that info was interesting for you. If It is, I will share the next some parameters I use for one of my env.

 

Cheers,

Gonchik Tsymzhitov

Comments

Post a Comment

Popular posts from this blog

Overview and practical use cases with open source tracing tool for Java Apps. Glowroot. Installation

-
Image
In that small article, you can find how to install the agent of Glowroot. Installation of the application is quite simple on agents, and this article shows a scheme for working with a built-in collector, but for industrial installations we use it with a bundle with elasticsearch. The installation can be both for individual nodes and so for the central collector. In this case, consider for a separate node. Prerequisites: {jira_home} - is location of Jira home directory. {jira_installation_directory} is the location of Jira installation directory.   Steps: Downloading the installer wget -c https://github.com/glowroot/glowroot/releases/download/v0.13.6/glowroot-0.13.6-dist.zip To check, create a directory via command   mkdir -p /{jira_home}/glowroot/tmp Let the Jira process write and set ownership for simplicity, but it is recommended that you just give the write ability to the owner of the Jira process. chown -R jira: /{jira_home}/glowroot We additionally set the argument to setenv.sh in
Read more

Atlassian Community, let's collaborate and provide stats to vendors about our SQL index usage

-
  Hi!  Gonchik is in touch. Today I would like to get a little bit of help from you related SQL indexes on your Jira installation (Data Center, Server edition does not matter).    I would like to share a story about  PostgreSQL  and  Jira 8.13.3  ( JSD 4.13.3 )  release.  In that post I will be happy if you answer and comment about your instance indexes, as those info can help to improve the existing situation of heavy indexes.  Typically, it starts from improvement of configuration (e.g. using  https://postgresqltuner.pl/ ),  then query analyzing, adding indexes, after removing as heavy one (shortly  https://wiki.postgresql.org/wiki/Index_Maintenance ) :)    I use like this query in PostgreSQL: SELECT s.schemaname,        s.relname AS tablename,        s.indexrelname AS indexname,        pg_size_pretty(pg_relation_size(s.indexrelid::regclass)) AS index_size,        idx_tup_read,         idx_tup_fetch,         idx_scan FROM pg_catalog.pg_stat_user_indexes s JOIN pg_catalog.pg_index i O
Read more

How only 2 parameters of PostgreSQL reduced anomaly of Jira Data Center nodes

-
Image
  Hello community, Gonchik Tsymzhitov is in touch. Today, I would like to share with you a short story about postgresqltuner.pl in usage.  So from previous articles I hope you configured the PostgreSQL server and postgresqltuner.pl.  After executing command, ./postgresqltuner.pl --ssd for ssd disks server. You can see like this output: postgresqltuner.pl version 1.0.1 [OK]      I can invoke executables Connecting to /var/run/postgresql:5432 database template1 as user 'postgres'... [OK]      The user account used by me for reporting has superuser rights on this PostgreSQL instance =====  OS information  ===== [INFO]    OS: linux Version: 5.4.17-2036.102.0.2.el8uek.x86_64 Arch: x86_64-linux-thread-multi [INFO]    OS total memory: 41.03 GB [OK]      vm.overcommit_memory is adequate: no memory overcommitment [INFO]    Running under a vmware hypervisor [INFO]    Currently used I/O scheduler(s): mq-deadline =====  General instance informations  ===== -----  PostgreSQL version  -----
Read more