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Re: [rvm-research] Call-Site Information
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From: Shoaib A. <shb...@gm...> - 2016-06-11 07:31:36
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Sorry Mike. I din’t state my question clearly enough. For some objects, the extra word in the MiscHeader I reserve for encoding the site id is never modified. It is the same value with what I initialized it with in MiscHeader.java. For others it is overwritten by either the instrumentation in the baseline or the optimizing compiler. > On Jun 11, 2016, at 1:06 AM, Michael Bond <mik...@cs...> wrote: > > Hi Shoaib, > > This sounds like the expected behavior: the value in an object's MiscHeader is preserved even after GC copies it. Are you wanting something else to happen? (If so, try modifying how copying in GC works; there are method that you can implement/modify called "postCopyAlloc" or something like that to modify what's in the MiscHeader.) > > If I'm missing the point, can you say what's the high-level thing you're trying to do? Maybe people on this list will have suggestions for what's the best way to do that. > > Cheers, > Mike > > On 06/10/2016 01:29 PM, Shoaib Akram wrote: >> Thanks Mike! I used the patch to encode the static allocation site ids in the object header. I added instrumentation code to both the baseline compiler and the optimizing compiler (BaselineCompilerImpl.java and opt/hir2lir/ExpandRuntimeServices.java), wherever new allocations are being handled. But for some objects, the allocation site id in MiscHeader at the end of the execution of programs is still the same value I used during initialization. I understand this happening for objects in the boot space But I don't see why this is happening to objects in the mature and the large space. Am I missing something? >> >> On Wed, May 25, 2016 at 4:10 AM, Michael Bond <mik...@cs... <mailto:mik...@cs...>> wrote: >> Hi Shoaib, >> >> Yes, this is definitely possible. There are two different ways to do it: >> >> (1) Insert instrumentation at compile time that "knows" the static allocation site. For example, during compile time, assign a unique integer for every allocation site, and generate instrumentation that writes that integer into the object header. >> >> (2) Insert instrumentation at compile time that figures out the allocation site at run time. It can do this by looking at the frame pointer and compiled method ID as you say; it gets a little bit complex with optimized code and inlining. >> >> My group's patch for calling context profiling ( <https://sourceforge.net/p/jikesrvm/research-archive/44/>https://sourceforge.net/p/jikesrvm/research-archive/44/ <https://sourceforge.net/p/jikesrvm/research-archive/44/>) has code related to both approaches. >> >> One gotcha: There's an issue in Jikes RVM (<=3.1.3, at least) such that if the left-most word (by default, this'll be the MiscHeader word) has the least-significant bit as 1 instead of 0, Jikes RVM will crash (at least with certain GCs?). You can avoid this by making sure it's always 0 or by putting the MiscHeader to the right of the TIB pointer; see our Octet patch for an example of the latter (https://sourceforge.net/p/jikesrvm/research-archive/43/ <https://sourceforge.net/p/jikesrvm/research-archive/43/>). >> >> Regarding your question about calling into Jikes RVM from MMTk: this is definitely possible, but it's required to go through a specific interface. See classes in org.mmtk.vm such as org.mmtk.vm.Barriers (an abstract method that has a Jikes RVM-specific implementation). You can add your own method to own of the these classes; the method can access Jikes RVM stuff but be called from MMTk. >> >> Cheers, >> Mike >> >> >> On 05/24/2016 02:28 PM, Shoaib Akram wrote: >>> Hi All, >>> >>> Hello from PerformanceLab @ Ghent University in Belgium. I want to ask if there is support in JikesRVM to identify the call-site of an allocation. Suppose I have the code below: >>> >>> 1 public IntersectionState() { >>> 2 stack = new StackNode[MAX_STACK_SIZE * 2]; >>> 3 for (int i = 0; i < stack.length; i++) >>> 4 stack[i] = new StackNode(); >>> 5 rstack = new float[53 * 256]; >>> 6 } >>> >>> Each time a new object is allocated (line no. 4 above), I want to store the call-site information (line 4) in the header of the object. Is it possible to get the unique identity of the method and index within the method, where a new object is being allocated from? >>> >>> There are some routines in runtime/Magic.java that let you get the current frame pointer or the id of the compiled method, but I am not sure if they usable from within MMTk(?) Does anyone know an an easy way to get the site information at allocation time? >>> >>> Thanks in advance! >>> >>> -- >>> Shoaib Akram >>> ELIS - Gent University >>> Belgium >>> >>> >>> ------------------------------------------------------------------------------ >>> Mobile security can be enabling, not merely restricting. Employees who >>> bring their own devices (BYOD) to work are irked by the imposition of MDM >>> restrictions. 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Make informed decisions using capacity > planning reports. https://ad.doubleclick.net/ddm/clk/305295220;132659582;e_______________________________________________ > Jikesrvm-researchers mailing list > Jik...@li... > https://lists.sourceforge.net/lists/listinfo/jikesrvm-researchers |