After a little research on the cause of high memory consumption while RSyntaxTree is running, I discovered that RMagick, which RSyntaxTree uses to render graphics, does not undertake garbage collection but the user needs to call GC.start every time the generated image has become unneeded. No wonder I had to reboot Mongrel so frequently!

Since RMagick 2.0 has been equipped with a newly introduced method Image#destroy!, a user-side garbage collection is quite easy. RSyntaxTree should be far more stable than it used to be. While the fact that my VPS capacity is quite limited does not go away, I’ll get the service back again and see how it goes.

RSyntaxTree のメモリ過消費の原因が分かりました。内部で使っているライブラリの RMagick がガベージコレクションをしてくれてなかったようです。一応、対策を施したので、ふたたびサービスを起動させようと思います。とはいえ、VPS のリソースが限られていることには変わりないので、これからも安定的に利用可能かどうかは分かりませんが・・・。