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Posted to dev@tomcat.apache.org by GitBox <gi...@apache.org> on 2019/03/06 15:15:38 UTC
[GitHub] [tomcat] philwebb commented on issue #143: Apply deduplication to
certain loaded and created Strings
philwebb commented on issue #143: Apply deduplication to certain loaded and created Strings
URL: https://github.com/apache/tomcat/pull/143#issuecomment-470145284
Sure. I discovered these by using the "Inspections" feature from [YourKit](https://www.yourkit.com/) on an [embedded Tomcat application](https://github.com/spring-projects/spring-boot/tree/87d696d6971c8bbd28be4fa885f9cf5719309c99/spring-boot-samples/spring-boot-sample-tomcat).
Without the change YourKit reports 2192 duplicate Strings, with the change it's 1126 (so a saving of 1066). It's hard to get the exact memory saving but scanning the UI for the top hitters we have:
| String | Duplicates | Waste
| --- | --- | -- |
"java.lang.String" | 2192 | 149112 |
"ACTION" | 542 | 38952 |
"boolean" | 191 | 10640 |
"void" | 204 | 9744 |
"Introspected parameter param0" | 80 | 8216 |
"int" | 155 | 7392 |
"[Ljava.lang.String;" | 42 | 3280 |
So it looks like at least 227336 bytes can be saved.
One other thing to consider is that I think these Strings are retained for the life of the application. They can't be GC'd because references remain until shutdown.
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