--- On Sun, 2/21/10, Adam Heath <doo...@brainfood.com> wrote: > From: Adam Heath <doo...@brainfood.com> > Subject: FlexibleStringExpander is still using too much memory > To: dev@ofbiz.apache.org > Date: Sunday, February 21, 2010, 12:18 PM > Recently, Adrian decided to alter FSE > to use less memory. He did this > by modifying the class to store a single char[], which > represented the > text contained by the FSE instance. However, this > change had the > opposite effect. > > Taken by itself, it made the class take up less memory, > this is true. > However, when considering that there could be sub-classes > that have > to parse sub-parts of the original string, each > sub-instance would > have it's very own copy of the internal chars that were in > the parent > string. > > Additionally, when the cache is in use, the memory doubles, > because > the original String key, containing the original array of > chars, is > kept around. > > Switching each instance back to String usage won't help; > while calling > String.subString may allow the internal array to be shared, > it's not > guaranteed. And, we'll still have the hit of the > stored String's > internal hashCode variable(4 bytes), not to mention the > additional > pointer to the string(another 4 bytes). > > There are additional memory usage issues, when the sub > classes taking > the original string/array, then concatenating the > open/close brackets, > thereby causing a new String to be created. > > I'm working on fixing all these issues, before I continue > on fixing 3486.
The specific memory use I tried to address was when an expression wasn't an expression - it was just a plain string. In those cases instead of taking up the space of a String object, you were taking up the space of the String object, plus a List, plus the FSE. Those FSE-wrapped String constants are then kept in memory via the various model classes. To test this concept, I created a counter to count how many non-expression FSEs were created, then visited the artifact info page. More than 78,000 instances were created. I might be missing something, or maybe I'm misunderstanding what you're saying, but it seems like you're saying there are memory issues with the cases where there *is* an expression (the ones that are cached). Those instances total a few thousand, and as you mentioned previously, they aren't taking up much memory. -Adrian
