jstat LGCC column shows
Yasumasa Suenaga
suenaga.yasumasa at oss.ntt.co.jp
Tue Jan 25 01:02:37 UTC 2011
Hi,
I made a patch for resolving this problem and attached it to this email.
I hope to discuss this problem.
Thanks.
(2011/01/04 13:11), Yasumasa Suenaga wrote:
> Hi,
>
> I ran SPECjvm2008 with OpenJDK6 provided by Fedora14 and Ubuntu 10.10 .
> I got following messages when I attached jstat to that VM with "-gccause" option:
>
> ------------
> root at ubuntu10:~# jstat -gccause 8411 500
> S0 S1 E O P YGC YGCT FGC FGCT GCT LGCC GCC
> 0.00 0.00 12.11 12.65 31.36 1 0.005 2 0.037 0.042 System.gc() No GC
> 0.00 0.00 12.11 12.65 31.36 1 0.005 2 0.037 0.042 System.gc() No GC
>
> -- snip --
>
> 0.00 0.00 76.81 12.65 31.58 1 0.005 2 0.037 0.042 System.gc() No GC
> 42.20 0.00 0.00 12.65 33.10 4 0.011 2 0.037 0.047 unknown GCCause No GC
> 91.06 0.00 0.00 15.12 34.10 10 0.019 2 0.037 0.056 unknown GCCause No GC
>
> -- snip --
>
> ------------
>
> "LGCC" column shows "unknown GCCause".
> I want to get "REAL" last gccause (I want to know what happened in VM, relating to GC).
> (In this case, I guess that LGCC shows "Allocation Failure".)
>
>
> I found the comment in constructor of VM_GC_Operation class as following:
> (OpenJDK7 (HS20) and OpenJDK6(HS19) are similar.)
>
> ------------
> // A subclass constructor will likely overwrite the following
> _gc_cause = GCCause::_no_cause_specified;
> ------------
>
>
> I checked constructor of subclass of VM_GC_Operation, and following classes do not
> initialize "_gc_cause" member:
>
> - VM_HeapDumper
> - VM_GC_HeapInspection
> - VM_GenCollectForAllocation
> - VM_G1OperationWithAllocRequest
> - VM_ParallelGCFailedAllocation
> - VM_ParallelGCFailedPermanentAllocation
>
> I think that we should initialize "_gc_cause" in constructor of these classes.
>
>
> Best regards,
>
>
--
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E-mail: suenaga.yasumasa at oss.ntt.co.jp
-------------- next part --------------
diff -r 102466e70deb src/share/vm/gc_implementation/g1/vm_operations_g1.hpp
--- a/src/share/vm/gc_implementation/g1/vm_operations_g1.hpp Thu Jan 20 15:52:05 2011 -0800
+++ b/src/share/vm/gc_implementation/g1/vm_operations_g1.hpp Tue Jan 25 09:39:32 2011 +0900
@@ -45,7 +45,9 @@
VM_G1OperationWithAllocRequest(unsigned int gc_count_before,
size_t word_size)
: VM_GC_Operation(gc_count_before),
- _word_size(word_size), _result(NULL), _pause_succeeded(false) { }
+ _word_size(word_size), _result(NULL), _pause_succeeded(false) {
+ _gc_cause = GCCause::_g1_alloc_request;
+ }
HeapWord* result() { return _result; }
bool pause_succeeded() { return _pause_succeeded; }
};
diff -r 102466e70deb src/share/vm/gc_implementation/parallelScavenge/vmPSOperations.cpp
--- a/src/share/vm/gc_implementation/parallelScavenge/vmPSOperations.cpp Thu Jan 20 15:52:05 2011 -0800
+++ b/src/share/vm/gc_implementation/parallelScavenge/vmPSOperations.cpp Tue Jan 25 09:39:32 2011 +0900
@@ -39,6 +39,7 @@
_is_tlab(is_tlab),
_result(NULL)
{
+ _gc_cause = GCCause::_allocation_failure;
}
void VM_ParallelGCFailedAllocation::doit() {
@@ -64,6 +65,7 @@
_size(size),
_result(NULL)
{
+ _gc_cause = GCCause::_allocation_failure;
}
void VM_ParallelGCFailedPermanentAllocation::doit() {
diff -r 102466e70deb src/share/vm/gc_implementation/shared/vmGCOperations.hpp
--- a/src/share/vm/gc_implementation/shared/vmGCOperations.hpp Thu Jan 20 15:52:05 2011 -0800
+++ b/src/share/vm/gc_implementation/shared/vmGCOperations.hpp Tue Jan 25 09:39:32 2011 +0900
@@ -137,6 +137,7 @@
VM_GC_Operation(0 /* total collections, dummy, ignored */,
0 /* total full collections, dummy, ignored */,
request_full_gc) {
+ _gc_cause = GCCause::_heap_inspection;
_out = out;
_full_gc = request_full_gc;
_need_prologue = need_prologue;
@@ -162,6 +163,7 @@
: VM_GC_Operation(gc_count_before),
_size(size),
_tlab(tlab) {
+ _gc_cause = GCCause::_collect_for_allocation;
_res = NULL;
}
~VM_GenCollectForAllocation() {}
diff -r 102466e70deb src/share/vm/gc_interface/gcCause.cpp
--- a/src/share/vm/gc_interface/gcCause.cpp Thu Jan 20 15:52:05 2011 -0800
+++ b/src/share/vm/gc_interface/gcCause.cpp Tue Jan 25 09:39:32 2011 +0900
@@ -48,6 +48,9 @@
case _allocation_failure:
return "Allocation Failure";
+ case _collect_for_allocation:
+ return "Collect for Allocation";
+
case _gc_locker:
return "GCLocker Initiated GC";
@@ -81,6 +84,9 @@
case _g1_inc_collection_pause:
return "G1 Evacuation Pause";
+ case _g1_alloc_request:
+ return "G1 Allocation Request";
+
case _last_ditch_collection:
return "Last ditch collection";
diff -r 102466e70deb src/share/vm/gc_interface/gcCause.hpp
--- a/src/share/vm/gc_interface/gcCause.hpp Thu Jan 20 15:52:05 2011 -0800
+++ b/src/share/vm/gc_interface/gcCause.hpp Tue Jan 25 09:39:32 2011 +0900
@@ -51,6 +51,7 @@
_no_gc,
_no_cause_specified,
_allocation_failure,
+ _collect_for_allocation,
/* implementation specific */
@@ -66,6 +67,7 @@
_adaptive_size_policy,
_g1_inc_collection_pause,
+ _g1_alloc_request,
_last_ditch_collection,
_last_gc_cause
diff -r 102466e70deb src/share/vm/services/heapDumper.cpp
--- a/src/share/vm/services/heapDumper.cpp Thu Jan 20 15:52:05 2011 -0800
+++ b/src/share/vm/services/heapDumper.cpp Tue Jan 25 09:39:32 2011 +0900
@@ -1390,6 +1390,7 @@
VM_GC_Operation(0 /* total collections, dummy, ignored */,
0 /* total full collections, dummy, ignored */,
gc_before_heap_dump) {
+ _gc_cause = GCCause::_heap_dump;
_local_writer = writer;
_gc_before_heap_dump = gc_before_heap_dump;
_is_segmented_dump = false;
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