G1 root cause and tuning
Medan Gavril
gabi_io at yahoo.com
Mon Apr 6 09:26:16 UTC 2015
Hi Charlie,
Our goal is to reduce number of Full GC as well as make them shorter by tuning G1. Of course we will check the application code in parallel.
we will start with
"XX:G1HeapRegionSize=8M”
then
UnlockExperimentalVMOptions
InitiatingHeapOccupancyPercent=0G1HeapWastePercent
Best Regards,Gabi Medan
On Friday, April 3, 2015 4:46 PM, charlie hunt <charlie.hunt at oracle.com> wrote:
Currently out the office. Perhaps Jenny and Thomas can chime in with some additional analysis.
To answer your specific questions, PrintHeapAtGCExtended is printing what we expect to see.Iirc, "no shared space configured" may be related to the AppCDS feature. We don't need to worry about that for your issues.Eden space size. No, we should not increase it. It looks the major issue is frequent humongous object allocations. Doing tests with increased region size would be the appropriate next steps.
Some additional observations from the log snippets ...Pause times in non-full GCs look to be in Update RS. Ideally we would want to largest amount of time to be in copy time. Reference processing times are kinda high too. Is your application using a large number of reference objects?One thing that's puzzling in the Full GC line is the amount of usr CPU time is much less than the real time. This seems odd! Could your system be paging to virtual memory? Or, if you are on Linux, do you have transparent huge pages enable (they should be disabled!). Also seeing more than 5 seconds in sys time is eye catching and could be related to the above issues.
All the above said, I think the major issue that needs to be addressed is the frequent large object allocations. If increasing region size doesn't address this, then you are likely looking at making application changes to remove the frequent large object allocations. Once that is addressed, we can focus on some of the other issues.
Charlie
Sent from my iPhone
On Apr 3, 2015, at 3:11 AM, Medan Gavril <gabi_io at yahoo.com> wrote:
HI Charlie,
We had today a FUL GC of 280 seconds. At least it printed the full gc and it did not end with a jvm hung. . We will apply XX:G1HeapRegionSize=8M. "XX:+PrintHeapAtGCExtended" did it printed the expected output?NO shared space configured, what does it mean? You said eden sapce is 1 GB. Can/should we increase it?
495364.337: [GC pause (young) 495364.337: [G1Ergonomics (CSet Construction) start choosing CSet, predicted base time: 258.26 ms, remaining time: 2241.74 ms, target pause time: 2500.00 ms] 495364.337: [G1Ergonomics (CSet Construction) add young regions to CSet, eden: 239 regions, survivors: 18 regions, predicted young region time: 63.39 ms] 495364.337: [G1Ergonomics (CSet Construction) finish choosing CSet, eden: 239 regions, survivors: 18 regions, old: 0 regions, predicted pause time: 321.65 ms, target pause time: 2500.00 ms], 0.25714812 secs] [Parallel Time: 181.0 ms] [GC Worker Start (ms): 495364337.4 495364337.4 495364337.4 495364337.4 495364337.5 495364337.5 495364337.5 495364337.5 495364337.5 495364337.5 495364337.5 495364337.5 495364337.5 Avg: 495364337.5, Min: 495364337.4, Max: 495364337.5, Diff: 0.1] [Ext Root Scanning (ms): 18.5 18.0 18.8 25.0 17.9 17.9 18.3 19.2 17.8 25.1 18.9 26.4 18.3 Avg: 20.0, Min: 17.8, Max: 26.4, Diff: 8.6] [SATB Filtering (ms): 0.0 0.0 0.0 0.0 0.0 1.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Avg: 0.1, Min: 0.0, Max: 1.3, Diff: 1.3] [Update RS (ms): 129.9 130.5 131.0 124.7 130.0 129.1 129.2 129.0 139.2 122.5 129.2 121.2 126.1 Avg: 128.6, Min: 121.2, Max: 139.2, Diff: 18.0] [Processed Buffers : 44 57 70 66 67 50 70 54 71 47 59 46 34 Sum: 735, Avg: 56, Min: 34, Max: 71, Diff: 37] [Scan RS (ms): 0.2 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.0 0.1 0.1 0.2 0.1 Avg: 0.1, Min: 0.0, Max: 0.2, Diff: 0.2] [Object Copy (ms): 26.9 27.0 25.6 25.7 27.3 27.1 27.9 27.2 18.4 27.7 27.3 27.6 30.8 Avg: 26.7, Min: 18.4, Max: 30.8, Diff: 12.4] [Termination (ms): 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0] [Termination Attempts : 2 3 3 1 3 3 3 3 3 2 3 1 2 Sum: 32, Avg: 2, Min: 1, Max: 3, Diff: 2] [GC Worker End (ms): 495364512.9 495364512.9 495364512.9 495364512.9 495364512.9 495364513.0 495364513.0 495364512.9 495364512.9 495364512.9 495364512.9 495364512.9 495364513.0 Avg: 495364512.9, Min: 495364512.9, Max: 495364513.0, Diff: 0.1] [GC Worker (ms): 175.5 175.5 175.5 175.5 175.5 175.5 175.5 175.4 175.4 175.4 175.4 175.4 175.4 Avg: 175.5, Min: 175.4, Max: 175.5, Diff: 0.1] [GC Worker Other (ms): 5.5 5.5 5.5 5.5 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 Avg: 5.6, Min: 5.5, Max: 5.6, Diff: 0.1] [Complete CSet Marking: 0.0 ms] [Clear CT: 0.3 ms] [Other: 75.9 ms] [Choose CSet: 0.0 ms] [Ref Proc: 72.8 ms] [Ref Enq: 0.4 ms] [Free CSet: 1.3 ms] [Eden: 956M(952M)->0B(972M) Survivors: 72M->52M Heap: 10420M(22480M)->9469M(22480M)] [Times: user=2.92 sys=0.00, real=0.27 secs] Total time for which application threads were stopped: 0.2605235 secondsTotal time for which application threads were stopped: 0.0024983 secondsTotal time for which application threads were stopped: 0.0046328 seconds 495368.172: [G1Ergonomics (Heap Sizing) attempt heap expansion, reason: humongous allocation request failed, allocation request: 134217744 bytes] 495368.172: [G1Ergonomics (Heap Sizing) expand the heap, requested expansion amount: 125829120 bytes, attempted expansion amount: 125829120 bytes] 495368.172: [G1Ergonomics (Heap Sizing) did not expand the heap, reason: heap expansion operation failed] 495368.176: [G1Ergonomics (Heap Sizing) attempt heap expansion, reason: humongous allocation request failed, allocation request: 134217744 bytes] 495368.176: [G1Ergonomics (Heap Sizing) expand the heap, requested expansion amount: 125829120 bytes, attempted expansion amount: 125829120 bytes] 495368.176: [G1Ergonomics (Heap Sizing) did not expand the heap, reason: heap expansion operation failed]495368.176: [GC pause (young) 495368.176: [G1Ergonomics (CSet Construction) start choosing CSet, predicted base time: 667.90 ms, remaining time: 1832.10 ms, target pause time: 2500.00 ms] 495368.176: [G1Ergonomics (CSet Construction) add young regions to CSet, eden: 243 regions, survivors: 13 regions, predicted young region time: 46.78 ms] 495368.176: [G1Ergonomics (CSet Construction) finish choosing CSet, eden: 243 regions, survivors: 13 regions, old: 0 regions, predicted pause time: 714.67 ms, target pause time: 2500.00 ms], 0.36436765 secs] [Parallel Time: 273.1 ms] [GC Worker Start (ms): 495368176.0 495368176.0 495368176.0 495368176.0 495368176.0 495368176.0 495368176.0 495368176.0 495368176.0 495368176.0 495368176.1 495368176.1 495368176.1 Avg: 495368176.0, Min: 495368176.0, Max: 495368176.1, Diff: 0.1] [Ext Root Scanning (ms): 23.1 19.7 25.1 21.5 21.6 25.3 18.7 19.3 25.5 20.5 18.4 20.6 20.1 Avg: 21.5, Min: 18.4, Max: 25.5, Diff: 7.2] [SATB Filtering (ms): 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.3 0.0 0.0 0.0 0.0 0.0 Avg: 0.1, Min: 0.0, Max: 1.3, Diff: 1.3] [Update RS (ms): 222.1 225.3 220.2 224.8 223.8 222.8 222.6 224.9 220.0 225.4 232.7 231.0 225.2 Avg: 224.7, Min: 220.0, Max: 232.7, Diff: 12.7] [Processed Buffers : 139 200 242 206 182 154 151 211 149 162 189 222 123 Sum: 2330, Avg: 179, Min: 123, Max: 242, Diff: 119] [Scan RS (ms): 0.0 0.3 0.0 0.0 0.0 0.0 0.2 0.2 0.0 0.0 0.0 0.0 0.0 Avg: 0.1, Min: 0.0, Max: 0.3, Diff: 0.3] [Object Copy (ms): 22.4 22.3 22.3 21.3 22.2 19.5 26.0 21.9 22.0 21.6 16.4 15.9 22.2 Avg: 21.2, Min: 15.9, Max: 26.0, Diff: 10.1] [Termination (ms): 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Avg: 0.0, Min: 0.0, Max: 0.0, Diff: 0.0] [Termination Attempts : 1 1 1 1 1 1 1 1 1 1 1 1 1 Sum: 13, Avg: 1, Min: 1, Max: 1, Diff: 0] [GC Worker End (ms): 495368443.7 495368443.6 495368443.6 495368443.7 495368443.7 495368443.6 495368443.7 495368443.6 495368443.6 495368443.7 495368443.7 495368443.6 495368443.7 Avg: 495368443.7, Min: 495368443.6, Max: 495368443.7, Diff: 0.1] [GC Worker (ms): 267.7 267.6 267.6 267.6 267.7 267.6 267.6 267.6 267.6 267.6 267.6 267.6 267.6 Avg: 267.6, Min: 267.6, Max: 267.7, Diff: 0.1] [GC Worker Other (ms): 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.6 5.6 5.6 Avg: 5.5, Min: 5.5, Max: 5.6, Diff: 0.1] [Complete CSet Marking: 0.0 ms] [Clear CT: 0.2 ms] [Other: 91.0 ms] [Choose CSet: 0.0 ms] [Ref Proc: 89.0 ms] [Ref Enq: 0.0 ms] [Free CSet: 1.4 ms] [Eden: 972M(972M)->0B(972M) Survivors: 52M->52M Heap: 10695M(22480M)->9727M(22480M)] [Times: user=3.74 sys=0.00, real=0.37 secs] 495368.541: [G1Ergonomics (Heap Sizing) attempt heap expansion, reason: humongous allocation request failed, allocation request: 134217744 bytes] 495368.541: [G1Ergonomics (Heap Sizing) expand the heap, requested expansion amount: 125829120 bytes, attempted expansion amount: 125829120 bytes] 495368.541: [G1Ergonomics (Heap Sizing) did not expand the heap, reason: heap expansion operation failed]Total time for which application threads were stopped: 0.3686524 seconds 495368.556: [G1Ergonomics (Heap Sizing) attempt heap expansion, reason: humongous allocation request failed, allocation request: 134217744 bytes] 495368.557: [G1Ergonomics (Heap Sizing) expand the heap, requested expansion amount: 125829120 bytes, attempted expansion amount: 125829120 bytes] 495368.557: [G1Ergonomics (Heap Sizing) did not expand the heap, reason: heap expansion operation failed] 495368.557: [G1Ergonomics (Heap Sizing) attempt heap expansion, reason: allocation request failed, allocation request: 134217744 bytes] 495368.557: [G1Ergonomics (Heap Sizing) expand the heap, requested expansion amount: 134217744 bytes, attempted expansion amount: 138412032 bytes] 495368.557: [G1Ergonomics (Heap Sizing) did not expand the heap, reason: heap expansion operation failed]495368.557: [Full GC 9731M->6801M(22480M), 283.4340824 secs] [Times: user=78.98 sys=5.43, real=283.44 secs] Total time for which application threads were stopped: 283.4511972 secondsTotal time for which application threads were stopped: 0.4082000 seconds495652.564: [GC concurrent-mark-abort]Total time for which application threads were stopped: 0.0152932 secondsTotal time for which application threads were stopped: 0.0434217 secondsTotal time for which application threads were stopped: 0.3351899 secondsTotal time for which application threads were stopped: 0.0395479 secondsTotal time for which application threads were stopped: 0.1017198 seconds
Total time for which application threads were stopped: 0.0664623 secondsTotal time for which application threads were stopped: 0.0095970 secondsTotal time for which application threads were stopped: 0.0200670 secondsTotal time for which application threads were stopped: 0.0033661 secondsTotal time for which application threads were stopped: 0.0029946 secondsTotal time for which application threads were stopped: 0.0726447 secondsTotal time for which application threads were stopped: 0.0023253 secondsTotal time for which application threads were stopped: 0.0050572 secondsTotal time for which application threads were stopped: 0.0861142 secondsTotal time for which application threads were stopped: 0.0025415 secondsTotal time for which application threads were stopped: 0.0028936 secondsTotal time for which application threads were stopped: 0.0096976 secondsTotal time for which application threads were stopped: 0.0025880 secondsTotal time for which application threads were stopped: 0.0116163 secondsTotal time for which application threads were stopped: 0.0026818 secondsTotal time for which application threads were stopped: 0.0032141 secondsTotal time for which application threads were stopped: 0.0078230 secondsTotal time for which application threads were stopped: 0.0025152 secondsTotal time for which application threads were stopped: 0.0026890 secondsTotal time for which application threads were stopped: 0.0030924 secondsTotal time for which application threads were stopped: 0.0027699 secondsTotal time for which application threads were stopped: 0.0029259 secondsTotal time for which application threads were stopped: 0.0032893 secondsTotal time for which application threads were stopped: 0.0037969 secondsTotal time for which application threads were stopped: 0.0130588 secondsTotal time for which application threads were stopped: 0.1230765 secondsTotal time for which application threads were stopped: 0.0022368 secondsTotal time for which application threads were stopped: 0.0022032 secondsTotal time for which application threads were stopped: 0.0505220 secondsTotal time for which application threads were stopped: 0.0351524 secondsTotal time for which application threads were stopped: 0.0022816 secondsTotal time for which application threads were stopped: 0.0292614 secondsTotal time for which application threads were stopped: 0.0117505 secondsTotal time for which application threads were stopped: 0.0035653 secondsTotal time for which application threads were stopped: 0.0388754 secondsTotal time for which application threads were stopped: 0.0028810 secondsTotal time for which application threads were stopped: 0.0025892 secondsTotal time for which application threads were stopped: 0.0028770 secondsTotal time for which application threads were stopped: 0.0024385 secondsTotal time for which application threads were stopped: 0.0025007 secondsTotal time for which application threads were stopped: 0.0024033 secondsTotal time for which application threads were stopped: 0.0024441 secondsTotal time for which application threads were stopped: 0.0028249 secondsTotal time for which application threads were stopped: 0.0026523 secondsTotal time for which application threads were stopped: 0.0025650 secondsTotal time for which application threads were stopped: 0.0025241 secondsTotal time for which application threads were stopped: 0.0026102 secondsTotal time for which application threads were stopped: 0.0026741 secondsTotal time for which application threads were stopped: 0.0025973 secondsTotal time for which application threads were stopped: 0.0027808 secondsTotal time for which application threads were stopped: 0.0112295 secondsTotal time for which application threads were stopped: 0.0028798 secondsTotal time for which application threads were stopped: 0.0026709 secondsTotal time for which application threads were stopped: 0.0038697 secondsTotal time for which application threads were stopped: 0.0026591 secondsTotal time for which application threads were stopped: 0.0025443 secondsTotal time for which application threads were stopped: 0.0040415 secondsTotal time for which application threads were stopped: 0.0025476 secondsTotal time for which application threads were stopped: 0.0025682 secondsTotal time for which application threads were stopped: 0.0032743 secondsTotal time for which application threads were stopped: 0.0034255 secondsTotal time for which application threads were stopped: 0.0034190 secondsTotal time for which application threads were stopped: 0.0025161 secondsTotal time for which application threads were stopped: 0.0036486 secondsTotal time for which application threads were stopped: 0.0034647 secondsTotal time for which application threads were stopped: 0.0032177 secondsTotal time for which application threads were stopped: 0.0027416 secondsTotal time for which application threads were stopped: 0.0034942 secondsTotal time for which application threads were stopped: 0.0026935 secondsTotal time for which application threads were stopped: 0.0029138 secondsTotal time for which application threads were stopped: 0.0026070 secondsTotal time for which application threads were stopped: 0.0025387 secondsTotal time for which application threads were stopped: 0.0145426 secondsTotal time for which application threads were stopped: 0.0031826 secondsTotal time for which application threads were stopped: 0.0023891 secondsTotal time for which application threads were stopped: 0.0027578 secondsTotal time for which application threads were stopped: 0.0742630 secondsTotal time for which application threads were stopped: 0.0024304 secondsTotal time for which application threads were stopped: 0.0637979 secondsTotal time for which application threads were stopped: 0.0198993 secondsTotal time for which application threads were stopped: 0.0491918 secondsTotal time for which application threads were stopped: 0.0024178 secondsTotal time for which application threads were stopped: 0.0098973 secondsTotal time for which application threads were stopped: 0.0302448 secondsTotal time for which application threads were stopped: 0.0121276 secondsTotal time for which application threads were stopped: 0.0025787 secondsTotal time for which application threads were stopped: 0.0138264 secondsTotal time for which application threads were stopped: 0.0153000 secondsTotal time for which application threads were stopped: 0.0027456 secondsTotal time for which application threads were stopped: 0.0038677 secondsTotal time for which application threads were stopped: 0.0029987 secondsTotal time for which application threads were stopped: 0.0054323 secondsTotal time for which application threads were stopped: 0.0026236 secondsTotal time for which application threads were stopped: 0.0034756 secondsTotal time for which application threads were stopped: 0.0028228 secondsTotal time for which application threads were stopped: 0.0096895 secondsTotal time for which application threads were stopped: 0.0028705 secondsTotal time for which application threads were stopped: 0.0038539 secondsTotal time for which application threads were stopped: 0.0027335 secondsTotal time for which application threads were stopped: 0.0039392 secondsTotal time for which application threads were stopped: 0.0030043 secondsTotal time for which application threads were stopped: 0.0025136 secondsTotal time for which application threads were stopped: 0.0041170 secondsTotal time for which application threads were stopped: 0.0134016 secondsTotal time for which application threads were stopped: 0.0028604 secondsTotal time for which application threads were stopped: 0.0030666 secondsTotal time for which application threads were stopped: 0.0092635 secondsTotal time for which application threads were stopped: 0.0035233 secondsTotal time for which application threads were stopped: 0.0027291 secondsTotal time for which application threads were stopped: 0.0026195 secondsTotal time for which application threads were stopped: 0.0025989 secondsTotal time for which application threads were stopped: 0.0027949 secondsTotal time for which application threads were stopped: 0.0035386 secondsTotal time for which application threads were stopped: 0.0034117 secondsTotal time for which application threads were stopped: 0.0033919 secondsTotal time for which application threads were stopped: 0.0024518 secondsTotal time for which application threads were stopped: 0.0031862 secondsTotal time for which application threads were stopped: 0.0032185 secondsTotal time for which application threads were stopped: 0.0028277 secondsTotal time for which application threads were stopped: 0.0032185 secondsTotal time for which application threads were stopped: 0.0034893 secondsTotal time for which application threads were stopped: 0.0027493 secondsTotal time for which application threads were stopped: 0.0031793 secondsTotal time for which application threads were stopped: 0.0041045 secondsTotal time for which application threads were stopped: 0.0025815 secondsTotal time for which application threads were stopped: 0.0035859 secondsTotal time for which application threads were stopped: 0.0038022 secondsTotal time for which application threads were stopped: 0.0029696 secondsTotal time for which application threads were stopped: 0.0037133 secondsTotal time for which application threads were stopped: 0.0032796 secondsTotal time for which application threads were stopped: 0.0030532 secondsTotal time for which application threads were stopped: 0.0026405 secondsTotal time for which application threads were stopped: 0.0033176 secondsTotal time for which application threads were stopped: 0.0032808 secondsTotal time for which application threads were stopped: 0.0200569 secondsTotal time for which application threads were stopped: 0.0027396 secondsTotal time for which application threads were stopped: 0.0037072 secondsTotal time for which application threads were stopped: 0.0024882 secondsTotal time for which application threads were stopped: 0.0030096 secondsTotal time for which application threads were stopped: 0.0024801 secondsTotal time for which application threads were stopped: 0.0025565 secondsTotal time for which application threads were stopped: 0.0038931 secondsTotal time for which application threads were stopped: 0.0030067 secondsTotal time for which application threads were stopped: 0.0030302 secondsTotal time for which application threads were stopped: 0.0271912 secondsTotal time for which application threads were stopped: 0.0026147 secondsHeap garbage-first heap total 23019520K, used 7803799K [0x0000000243000000, 0x00000007c0000000, 0x00000007c0000000) region size 4096K, 146 young (598016K), 0 survivors (0K) compacting perm gen total 258048K, used 255345K [0x00000007c0000000, 0x00000007cfc00000, 0x0000000800000000) the space 258048K, 98% used [0x00000007c0000000, 0x00000007cf95c610, 0x00000007cf95c800, 0x00000007cfc00000)No shared spaces configured.on_exit trigger matched. Restarting the JVM. (Exit code: -1)
On Tuesday, March 31, 2015 3:52 PM, charlie hunt <charlie.hunt at oracle.com> wrote:
Just as a clarification, the -XX:+ParallelRefProcEnabled will help reduce the time spent in reference processing. It will not help address the issue of seeing Full GCs as a result of frequent humongous object allocations, or a humongous allocations where there is not sufficient contiguous regions available to satisfy the humongous allocation request.
Thomas’s suggestion to increase the region size may help with the Full GCs as a result of humongous object allocations.
thanks,
charlie
On Mar 31, 2015, at 7:42 AM, Medan Gavril <gabi_io at yahoo.com> wrote:
HI Charlie,
Currenltly we can only go to java 7 update 7x(latest).
We will try the following changes: 1. -XX:G1HeapRegionSize=8 (then increase) 2. -XX:+ParallelRefProcEnabled
Please let me know if you have any other suggestion.
Best Regards,Gabi Medan
On Tuesday, March 31, 2015 3:35 PM, charlie hunt <charlie.hunt at oracle.com> wrote:
To add to Thomas’s good suggestions, I suppose one other alternative is to make application changes to break up the 300+ MB allocation into smaller MB allocations. This would offer a better opportunity for that humongous allocation to be satisfied.
hths,
charlie
On Mar 31, 2015, at 6:30 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
Hi all,
On Mon, 2015-03-30 at 20:41 -0500, charlie hunt wrote:
Hi Jenny,
One possibility is that there is not enough available contiguous
regions to satisfy a 300+ MB humongous allocation.
If we assume a 22 GB Java heap, (a little larger than the 22480M shown
in the log), with 2048 G1 regions (default as you know), the region
size would be about 11 MB. That implies there needs to be about 30
contiguous G1 regions available to satisfy the humongous allocation
request.
An unrelated question … do other GCs have a similar pattern of a
rather large percentage of time in Ref Proc relative to the overall
pause time, i.e. 24.7 ms / 120 ms ~ 20% of the pause time. If that’s
the case, then if -XX:+ParallelRefProcEnabled is not already set,
there may be some low hanging tuning fruit. But, it is not going to
address the frequent humongous allocation problem. It is also
interesting in that the pause time goal is 2500 ms, yet the actual
pause time is 120 ms, and eden is being sized at less than 1 GB out of
a 22 GB Java heap. Are the frequent humongous allocations messing
with the heap sizing heuristics?
While I have no solution for the problem we are aware of these problems:
- https://bugs.openjdk.java.net/browse/JDK-7068229 for dynamically
enabling MT reference processing
- https://bugs.openjdk.java.net/browse/JDK-8038487 to use mixed GC
instead of Full GC to clear out space for failing humoungous object
allocations.
I am not sure about what jdk release "JRE 1.17 update 17" actually is.
>From the given strings in the PrintGCDetails output, it seems to be
something quite old, I would guess jdk6?
In that case, if possible I would recommend trying a newer version that
improves humongous object handling significantly (e.g. 8u40 is latest
official).
Another option that works in all versions I am aware of is increasing
heap region size with -XX:G1HeapRegionSize=<X>M, where X is 8/16 or 32;
it seems that 4M region size has been chosen by ergonomics.
Start with the smaller of the suggested values.
Thanks,
Thomas
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