On an older phone originally designed to run Android 1.5 or 1.6, what are the pros and cons of using a newer Android feature like the JIT compiler?

  • As an example, I have an HTC Dream running CyanogenMod 6 and within the options you are able to choose whether to use the JIT or not. Elsewhere I have seen conflicting information on whether the JIT compiler will help or hurt the performance of an older phone. I tried to keep this question from being too phone-specific, as I think an answer to this could help clarify the issue on any older model phone, not just the Dream. – Mingo Feb 15 '11 at 7:46
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    Great question. The only thing I know about JIT is from my experience with Java/C#. Mostly that it waits to compile some code until run time and the JIT "smartly" caches code that it sees that repeats itself. Wiki might help explain better: en.wikipedia.org/wiki/Just-in-time_compilation – Bryan Denny Feb 15 '11 at 14:31

JIT typically causes an app to use more RAM due to the JIT cache, although Android's JIT was specifically designed so the additional memory usage was minimal (compared to a typical Java JIT). On phones that are already very RAM-starved to begin with, JIT may result in a decrease in performance.

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    This makes sense to me - my Dream is so limited when it comes to RAM that turning the JIT on really killed performance. However, I wonder about other older phones that aren't so short on RAM. – Mingo Feb 16 '11 at 0:34

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