Hi list, we are planing to port dalvikvm to a new cpu. we're worry about emulator issue because clearly qemu doesn't support own homebrew cpu. so i took a dirty investigation on the relationship between qemu- emulator-dalvik. could you go through my sum up and give me some comments?
The role of emulator in dalvik applications storing in android system in the form of apk(android package). actually it's a zip archive with some metadata. it contains a file named classes.dex. the file is compact to save storage. however, dex file can not execute directly after memory-mapped. it needs to transform to ODEX file, which O means "optimized" here. i think the name of ODEX is a little misleading since the phrase contains 3 purposes, while "optimization" is only one of them. i) realignment and byte-swapping. ii) verification dex code iii) optimization There're at least 3 different ways to get odex job done. i iterate them in chronicle order: i)[build-time] The building system does it ahead of time. ii)[install-time] The system installer does it when an application is first added(to device). iii)[run-time] The VM does it "just in time" It is the #1 choice needs the emulator, which will communicate with underlying QEMU. as doc said, The building system use a hairy process that involves the emulator , force JIT optimization of all relevant dex files and then extract the result from dalvik-cache. i don't know the exact meaning of "hairy" here. but i found the hairy process in android source. it is android/build/tools/dexpreopt/dexpreopt.py. The python script will spawn the emulator in shell form(no GUI like attachment), secretely run dexopt on it with dex files, and pull optimized results from emulator. In default, android building system performs dexpreopt for system-level java programs instead of applications. i also notices that it forbid the dexpreopt on Mac OSX, as the comments said in android/build/core/product_config.mk # Hack to make the linux build servers use dexpreopt. # OSX is still a little flaky. so i think we can skip choice #1 and leave dalvik perform dex-odex at install-time or runtime. it's clear that #2 and #3 occurs on real device. no emulator need. -- unsubscribe: android-porting+unsubscr...@googlegroups.com website: http://groups.google.com/group/android-porting
