JDK-6307570 : jmap performance and robustness improvement
  • Type: Bug
  • Component: core-svc
  • Sub-Component: tools
  • Affected Version: 6
  • Priority: P3
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2005-08-08
  • Updated: 2010-08-24
  • Resolved: 2005-08-17
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Other JDK 6
1.4.2_12Fixed 6 b48Fixed
Related Reports
Relates :  
JDK-5109224 - SA utilities: add heap dump option for jmap
Description
jmap heap dump facility should work at reasonable speed for large heap apps and core dumps.
Comments
EVALUATION The following improvements can be done: # cache InstanceKlass Field list and instance size and re-use it (instead of creating this for every Instance). # rewrite writePrimitiveArray - avoiding field walking by iterateFields (and Field object creations). primitive type sizes and array base offsets are read up-front and cached. # rewrite writeObjectArray - avoiding ObjectHeap.newOop for elements. -- all we want are addresses of elements and so reading OopHandles # Avoid calls to Symbol.asString calls for signature Symbols. Just looking at first char using getByteAt(0) instead. # While writing object/array fields of Instance objects, avoid ObjectHeap.newOop call and directly reading OopHandles. # avoid temp. file creation and file copy (use FileChannel and seek) # avoid second time walking of heap for Symbol (use explicit symbol table walking - using SymbolTable.symbolsDo) # explicit SystemDictionary walking to dump class (avoid classes list maintenance) # add dummy allocation site of zero frames - so that HAT can be run without -stack false option (renamed INVALID_STACK_TRACE_ID to DUMMY_STACK_TRACE_ID). Please refer to "suggested fix" as well.
10-08-2005
SUGGESTED FIX Initial version developed against 1.4.2/sa_baseline: http://bongo.india/debugging/sa/jmapdump-perf-robust/webrev/ 1.5.0/sa_baseline webrev is: http://bongo.india/debugging/sa/jmapdump-perf-robust/1.5.0/webrev 1.6.0 webrev is: http://bongo.india/debugging/sa/6307570/webrev/ Also, refer to attachment "webrev.tar"
10-08-2005