IntelliJ is very slow when handling big files

Question

I'm using Guidewire development Studio (IntelliJ-based IDE), and it is very slow when handling big text files (~ 1500 lines and above). I tried with an out-of-the-box community IntelliJ as well, but meet the same problem.

When I open those files, it takes 1 second to type a character, even when I see clearly that the used memory is still plenty (1441 MB/ 3959 MB). Also, it quickly suck up all the memory if I open multiple files (I allocate 4GB just for IntelliJ). Intellisense and other automatical stuff is painfully slow as well.

I love IntelliJ, but working in those condition is just so hard. Is there any way to work around this problem? I have thought of some alternatives, like:

1. Edit big files on another editor (eg: Notepad++), then reload it on IntelliJ
2. Open another small file, copy your bit of code there, edit it, then copy it back. It would help because intellisense and code highlight is maintained, however it is troublesome

I did turn off all unnecessary plugins, only leaving those necessary, but nothing improved much.

I am also wondering if I can "embed" some of outside editor in IntelliJ? Like Notepad++, Notepad2 for example? I did my homework and google around but find no plugins/ configuration that allow to do that.

Is there anyone who's experienced can give me some advices how to work with big files in IntelliJ (without going mad)?

UPDATE: Through my research I learn that IntelliJ can break for very large files (like 20mb) or so on. But my file isn't that big. It just have about 100KB - 1MB, but it's very long text.

UPDATE 2 After trying increase the heap memory as Sajidkhan advise (I changed both idea64.vmoptions and idea.vmoptions), I realize that somehow IntelliJ doesn't take the change. The memory heap is stuck at maximum 3GB.

On another note, the slow performance can be perceived when the system uses only around ~1GB of heap memory, so I think the problem doesn't relate to memory issue.

Answer 1

After a while working around the bush, I find a workaround, kind of.

When I check other answers from similar questions, I found that they begin get troubles when the file size is at least several MBs. It doesn't make sense, since I got the trouble when the files are only several KBs. After more careful checking, I found that the Gosu plugin is the culprit: after I mark my Gosu file as "text only", the speed becomes normal.

So I guess the problem has something to do with code highlighter & syntax reminder. For now, the best way I work-around this is:

1. Right-click the file and mark it as plain text.
2. Close the file and open it again, then edit.

Note: Since it applies for all the file type in Guidewire development suit, you may want to mark permanently some long files as plain text, especially the *.properties (aka, i18n/international files). The benefit of code auto-completer just doesn't worth the trouble.