xiaofeng, I have two major problems which need to be solved currently. 1. In my computer, Drlvm's java.exe couldn't run the java program which has loadLibrary call. I don't know whether it is for drlvm's reason or not. I don't know if others can run it correctly. It is a troublesome matter for me. 2. Is it proper to use MyRuntime which was refered yesterday to support the free(obj) in the early work which is lack of support of JIT? I planned to verify it by an test program. But for above reason, I couldn't go on now.
Thanks, tingpeng ----- Original Message ----- From: "Xiao-Feng Li" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, April 30, 2007 9:47 AM Subject: Re: problem about System.loadLibrary and object's address > Tingpeng, I think for first step test, you can use traditional JNI. > The fast JNI is only for performance here. > > Thanks, > xiaofeng > > On 4/29/07, Tingpeng Wu <[EMAIL PROTECTED]> wrote: >> xiaofeng, very thank you for your help and valuable time. I will try your >> suggestion next. >> ----- Original Message ----- >> From: "Xiao-Feng Li" <[EMAIL PROTECTED]> >> To: <[email protected]> >> Sent: Sunday, April 29, 2007 8:36 PM >> Subject: Re: problem about System.loadLibrary and object's address >> >> >> > On 4/29/07, LvJimmy，Jing <[EMAIL PROTECTED]> wrote: >> >> 2007/4/29, Tingpeng Wu <[EMAIL PROTECTED]>: >> >> > >> >> > ----- Original Message ----- >> >> > From: "LvJimmy，Jing" <[EMAIL PROTECTED]> >> >> > To: <[email protected]> >> >> > Sent: Sunday, April 29, 2007 5:24 PM >> >> > Subject: Re: problem about System.loadLibrary and object's address >> >> > >> >> > >> >> > > 2007/4/29, Tingpeng Wu <[EMAIL PROTECTED]>: >> >> > >> Hi, xiaofeng, >> >> > >> >> >> > >> 1. I also feel very unnatural to call it through MyRuntime class, >> >> > >> but I don't know how to call it directly. Since drlvm needs HotSpot >> >> > >> to help it to compile the java source code, if I don't call it >> >> > >> though an instance, the HotSpot couldn't distinguish it. If I let >> >> > >> the Jit to add the free() call in a future time, I will not need it >> >> > >> any more. >> >> > >> >> >> > > >> >> > > :) Java static method can be called as SomeClass.StaticMethod, so your >> >> > > program can be written as (it is nothing related with compiler) >> >> > > public static void main(String[] args) >> >> > > { >> >> > > set(10); >> >> > > System.out.println(get()); >> >> > > } >> >> > > >> >> > >> >> > >> 2. I added an method named "unsigned int get_object_addr(jobject >> >> > >> jobj)" in object_handle.cpp to return the address of jobj . I can >> >> > >> call it directly to get the object address in free() method. Since I >> >> > >> could not assure whether it can get the right address, so I add the >> >> > >> get_obj_addr() for test purpose. I will delete it if it can work >> >> > >> corredtly. >> >> > >> >> >> > > >> >> > > Ah, I don't catch well here. Why do you need a free() function here? >> >> > > If you alloc a java object (no matter in java or native), you can just >> >> > > leave it alone and let GC do everything for you. Free() is too c-style >> >> > > for Java developer :) >> >> > > In the other way, if you want to alloc some memory for other use, for >> >> > > an example, char array in c/c++, you can just keep its address(you can >> >> > > keep a jlong as void* ) and free it at last(you'd better free in this >> >> > > case or you'll get memory leak). It is such easier to keep/pass a >> >> > > jlong value than jobject handle. >> >> > > >> >> > My thesis is to redesign the heap layout, and provide the free() method >> >> > to support reclaiming the object explicitly. Then in jit module, I will >> >> > add some analysis to insert some free call to reclaim the dead object >> >> > in advance. The purpose is to try to improve the efficiency of >> >> > program's execution. >> >> > >> >> >> >> Got it, I remember we've already discussed this problem (free() in >> >> java) and IIRC, some expert mark this problem as "mission impossible" >> >> ... :) >> >> However study something about GC may benefit your thesis. :) >> > >> > Jimmy, it's possible to insert free() automatically in jitted code to >> > reclaim some short-lived objects. This can be a supplementary to the >> > GC, and probably improve the overall performance. Tingpeng had >> > previous discussions with me on this topic actually. >> > >> > TingPeng, the runtime helper is a way in DRLVM for the VM to provide >> > JIT certain supports, e.g., exception throwing, etc. One of the >> > important usages of runtime helper is to provide a way of fast native >> > method invocation. That is, when you know a native method never causes >> > GC, you probably can use a runtime helper for JIT to generate code to >> > invoke this native method directly without going through the JNI >> > stuff. This makes native call fast. >> > >> > You can find runtime helper code in jit_runtime_support related files. >> > Please go search VM_RT_AASTORE in vm source code, you will see in >> > vmcore/src/util/ia32/base/jit_runtime_support_ia32.cpp how aastore can >> > implemented in native code to support JIT. VM_RT_GC_HEAP_WRITE_REF >> > is an example for write barrier native implementation >> > gc_heap_slot_write_ref(). >> > >> > Please let me know if you have any further questions. >> > >> > Thanks. xiaofeng >> > >> >> > > >> >> > >> 3. Another quesetion: where is runtime helper you speak of? I am >> >> > >> afraid I need do some investigation on it. >> >> > >> >> >> > >> Thanks, >> >> > >> tingpeng >> >> > >> ----- Original Message ----- >> >> > >> From: "Xiao-Feng Li" <[EMAIL PROTECTED]> >> >> > >> To: <[email protected]> >> >> > >> Sent: Sunday, April 29, 2007 4:05 PM >> >> > >> Subject: Re: problem about System.loadLibrary and object's address >> >> > >> >> >> > >> >> >> > >> > Tingpeng, >> >> > >> > >> >> > >> > 1. Your native is static native, why do you call it through an >> >> > >> > instance? >> >> > >> > 2. You probably need to use runtime helper for the object direct >> >> > >> > free >> >> > >> > in Java app, because the default JNI call path will save the object >> >> > >> > handle (and passes the reference address as a root entry during GC >> >> > >> > enumeration). For your purpose, there is no GC happening in free(), >> >> > >> > so it probably works with a stale object reference (freed) in the >> >> > >> > object handle. >> >> > >> > 3. You can use free() directly to retrieve its object address from >> >> > >> > the >> >> > >> > handle. Why do you need the get_obj_addr() method? >> >> > >> > >> >> > >> > Thanks, >> >> > >> > xiaofeng >> >> > >> > >> >> > >> > On 4/29/07, Tingpeng Wu <[EMAIL PROTECTED]> wrote: >> >> > >> >> Thanks, xiaofeng, >> >> > >> >> My test program is simple as follows: >> >> > >> >> >> >> > >> >> public class JNItest >> >> > >> >> >> >> > >> >> { >> >> > >> >> >> >> > >> >> static >> >> > >> >> >> >> > >> >> { >> >> > >> >> >> >> > >> >> System.loadLibrary("goodluck"); >> >> > >> >> >> >> > >> >> } >> >> > >> >> >> >> > >> >> >> >> > >> >> >> >> > >> >> public native static int get(); >> >> > >> >> >> >> > >> >> public native static void set(int i); >> >> > >> >> >> >> > >> >> >> >> > >> >> >> >> > >> >> public static void main(String[] args) >> >> > >> >> >> >> > >> >> { >> >> > >> >> >> >> > >> >> JNItest test = new JNItest(); >> >> > >> >> >> >> > >> >> test.set(10); >> >> > >> >> >> >> > >> >> System.out.println(test.get()); >> >> > >> >> >> >> > >> >> } >> >> > >> >> >> >> > >> >> } >> >> > >> >> >> >> > >> >> Then I use javah to produce JNItest.h and implement two method in >> >> > >> >> JNItest.cpp. Then use them to build goodluck.dll. I use the >> >> > >> >> latest verson of drlvm to test it, there is still an error which >> >> > >> >> reports "Vm launcher meets error and needs shut up (this is >> >> > >> >> translated from chinese)". >> >> > >> >> >> >> > >> >> The reason I asked the second problem is I want to get the >> >> > >> >> address of obj in java to support the reclaimation. I plan to >> >> > >> >> MyRuntime class, which has a native method, >> >> > >> >> My thought now is as follows: >> >> > >> >> 1. provide a new class named MyRuntime which has two native >> >> > >> >> methods. >> >> > >> >> class MyRuntime >> >> > >> >> { >> >> > >> >> static >> >> > >> >> { >> >> > >> >> System.loadLibrary("runtime"); >> >> > >> >> } >> >> > >> >> >> >> > >> >> //public native static void alloc(……); >> >> > >> >> >> >> > >> >> public native static void get_obj_addr(Object obj); >> >> > >> >> >> >> > >> >> //public native static void free(Object obj); >> >> > >> >> } >> >> > >> >> >> >> > >> >> 2. export the get_object_addr(jobject jobj) in vmcore to >> >> > >> >> support MyRuntime.get_obj_addr(Object obj) >> >> > >> >> 3. export the free(unsigned size, void* address) in gc to >> >> > >> >> support MyRuntime.free(Object obj) >> >> > >> >> 4. if above is right, I can call MyRuntime.free(obj) in java >> >> > >> >> method. >> >> > >> >> >> >> > >> >> >> >> > >> >> >> >> > >> >> Is it feasible to get address that way to support the >> >> > >> >> reclaimation method? >> >> > >> >> >> >> > >> >> Thanks, >> >> > >> >> tingpeng >> >> > >> >> >> >> > >> >> ----- Original Message ----- >> >> > >> >> From: "Xiao-Feng Li" <[EMAIL PROTECTED]> >> >> > >> >> To: <[email protected]> >> >> > >> >> Sent: Sunday, April 29, 2007 11:06 AM >> >> > >> >> Subject: Re: problem about System.loadLibrary and object's address >> >> > >> >> >> >> > >> >> >> >> > >> >> > Tingpeng, can you post your program if there is no legal issue? >> >> > >> >> > (e.g., >> >> > >> >> > open a JIRA issue and attach your code there). >> >> > >> >> > >> >> > >> >> > For your second question, itis pretty the core part of JVM >> >> > >> >> > native >> >> > >> >> > interface design. Yes, the handle is used to access Java object >> >> > >> >> > indirectly. The idea is to support object movement during GC, >> >> > >> >> > then the >> >> > >> >> > real new address of the same object can be stored to the >> >> > >> >> > handle. It's >> >> > >> >> > not supposed to be used everywhere in the JVM, because that may >> >> > >> >> > break >> >> > >> >> > the protocol of JNI, causing GC to fail to update the object new >> >> > >> >> > address, e.g., if it is put into a register by your C compiler. >> >> > >> >> > You >> >> > >> >> > can access it in two ways: either always use JNI interface, or >> >> > >> >> > guarantee there is GC happening when you access it. >> >> > >> >> > >> >> > >> >> > Thanks, >> >> > >> >> > xiaofeng >> >> > >> >> > >> >> > >> >> > On 4/29/07, 吴廷鹏 <[EMAIL PROTECTED]> wrote: >> >> > >> >> >> Hi, all, >> >> > >> >> >> when I use drlvm to execute my program, I found that when >> >> > >> >> >> program has System.loadLibrary call, there is always an error >> >> > >> >> >> which reports "java.lang.outofmemoryerror <no stack trace >> >> > >> >> >> available>". The same program can run on Hotspot. Why this >> >> > >> >> >> happens and how to solve it? >> >> > >> >> >> >> >> > >> >> >> Another question, I read the implementation code of >> >> > >> >> >> Object.clone method in Object_generic.cpp. >> >> > >> >> >> >> >> > >> >> >> jobject object_clone(JNIEnv *jenv, jobject jobj) >> >> > >> >> >> { >> >> > >> >> >> ObjectHandle h = (ObjectHandle) jobj; >> >> > >> >> >> >> >> > >> >> >> //aquire the target address and assign it to variable >> >> > >> >> >> named result >> >> > >> >> >> >> >> > >> >> >> memcpy(result, h->object, size); >> >> > >> >> >> >> >> > >> >> >> } >> >> > >> >> >> According to my comprehension, h->object is the address of >> >> > >> >> >> java object. Is it ture? Does this means I can use the same >> >> > >> >> >> way to get the address of object in vmcore's other place >> >> > >> >> >> provided the necessary head file is included? >> >> > >> >> >> >> >> > >> >> >> Thanks, >> >> > >> >> >> tingpeng >> >> > >> >> >> >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > -- >> >> > >> >> > http://xiao-feng.blogspot.com >> >> > >> >> > >> >> > >> > >> >> > >> > >> >> > >> > -- >> >> > >> > http://xiao-feng.blogspot.com >> >> > >> > >> >> > > >> >> > > >> >> > > -- >> >> > > >> >> > > Best Regards! >> >> > > >> >> > > Jimmy, Jing Lv >> >> > > China Software Development Lab, IBM >> >> > > >> >> >> >> >> >> -- >> >> >> >> Best Regards! >> >> >> >> Jimmy, Jing Lv >> >> China Software Development Lab, IBM >> >> >> > >> > >> > -- >> > http://xiao-feng.blogspot.com >> > > > > -- > http://xiao-feng.blogspot.com >
