javascript is not java, which doesn't necesarily need a vm. It is dynamic, but not a vm based language
2014-05-12 0:34 GMT+08:00 李白|字一日 <[email protected]>: > please have a look at this. > http://www.reddit.com/comments/1jw6h7 > > seems dalvik is slower. > > 2014-05-11 22:28 GMT+08:00 Kristopher Micinski <[email protected]>: > > First of all, this is just downright false, JS *will* be slower than >> Java, but I'll address each of your points. >> >> On Sun, May 11, 2014 at 12:51 AM, 李白|字一日 <[email protected]> wrote: >> > thanks for the reply. >> > >> > but i may think differently. >> > >> > javascript runtime can be shared, and no new memory allocation and >> memory >> > copying required, only the apps require new memories when running. >> >> The Android runtime is also shared, common memory pages are mapped >> between processes. This is the idea behind the "zygote" process, >> which loads the VM in an initial process and then forks off new >> processes, and due to copy on write (among other things) the VM is >> never copied. >> >> Apps only require the new memory they need. You can't just slam them >> all together in the same process, because that will completely destroy >> security and that will never happen. By the way, the same thing >> exists in JavaScript for multiple JavaScript tabs. > > >> > but the android vm is not, at least you should allocation memory for >> > inter-media code files like .class files. >> > then allocate new memory for the vm and then allocate for the app. >> >> As I said, you don't allocate any new memory for the VM because of the >> zygote. You have to allocate pages to keep track of the code, but you >> also do this with JS, but it's way worse because you need extra stuff >> to do all the data structures for interpretation / JIT. >> >> > for java multi-threading, you may need extra memory to providing more >> stacks >> > and extra execution on how to coordinating the threads. >> > >> > but javascript may need only one thread, and no threads switching >> needed, it >> > is event based. >> >> You'll still need threads in JavaScript to make anything efficient. > > >> > webkit and javascript event model is native implemented (using c/c++) >> and vm >> > free, while java sdk is compiled in java code and interpreted to native. >> >> There are open source Java compilers. AOSP is open source. >> >> > html and javascript files are translated to native code or natived >> > implemented interpretors when loaded. >> >> The same thing happens right now. >> >> > so i think java is by no means faster than javascript, especially when >> you >> > have very complicated interactions. >> >> It's up for debate, but your arguments for it don't show this. >> >> There are tricks to make this work, >> http://en.wikipedia.org/wiki/Firefox_OS does them. >> >> However, JS doesn't have any inherent performance advantages over >> Java: it's slower if implemented badly. >> >> > From all the above, i would like to say that javascript is easy and >> fast to >> > load and run, while java is slow to load and run. >> > if that is true, i think that is the great performance gain. >> > >> > java server side is fast in that java programs have loaded and they are >> all >> > in memory and servers always provide large memory spaces, we can ignore >> the >> > loading and rebooting time it requires, but android is not for server >> side >> > programming, it may not have large memory space for too many apps and >> users >> > don't have patient to wait too long for starting a new app. >> >> Many apps are compiled natively or with a JIT, this is the exact same >> as JavaScript. >> >> Kris >> >> -- >> You received this message because you are subscribed to the Google >> Groups "Android Developers" group. >> To post to this group, send email to [email protected] >> To unsubscribe from this group, send email to >> [email protected] >> For more options, visit this group at >> http://groups.google.com/group/android-developers?hl=en >> --- >> You received this message because you are subscribed to a topic in the >> Google Groups "Android Developers" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/android-developers/4UrtNOPympc/unsubscribe >> . >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> >> -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en --- You received this message because you are subscribed to the Google Groups "Android Developers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
