G1 root cause and tuning
charlie hunt
charlie.hunt at oracle.com
Fri Apr 3 13:46:09 UTC 2015
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 seconds
> Total time for which application threads were stopped: 0.0024983 seconds
> Total 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 seconds
> Total time for which application threads were stopped: 0.4082000 seconds
> 495652.564: [GC concurrent-mark-abort]
> Total time for which application threads were stopped: 0.0152932 seconds
> Total time for which application threads were stopped: 0.0434217 seconds
> Total time for which application threads were stopped: 0.3351899 seconds
> Total time for which application threads were stopped: 0.0395479 seconds
> Total time for which application threads were stopped: 0.1017198 seconds
> Total time for which application threads were stopped: 0.0664623 seconds
> Total time for which application threads were stopped: 0.0095970 seconds
> Total time for which application threads were stopped: 0.0200670 seconds
> Total time for which application threads were stopped: 0.0033661 seconds
> Total time for which application threads were stopped: 0.0029946 seconds
> Total time for which application threads were stopped: 0.0726447 seconds
> Total time for which application threads were stopped: 0.0023253 seconds
> Total time for which application threads were stopped: 0.0050572 seconds
> Total time for which application threads were stopped: 0.0861142 seconds
> Total time for which application threads were stopped: 0.0025415 seconds
> Total time for which application threads were stopped: 0.0028936 seconds
> Total time for which application threads were stopped: 0.0096976 seconds
> Total time for which application threads were stopped: 0.0025880 seconds
> Total time for which application threads were stopped: 0.0116163 seconds
> Total time for which application threads were stopped: 0.0026818 seconds
> Total time for which application threads were stopped: 0.0032141 seconds
> Total time for which application threads were stopped: 0.0078230 seconds
> Total time for which application threads were stopped: 0.0025152 seconds
> Total time for which application threads were stopped: 0.0026890 seconds
> Total time for which application threads were stopped: 0.0030924 seconds
> Total time for which application threads were stopped: 0.0027699 seconds
> Total time for which application threads were stopped: 0.0029259 seconds
> Total time for which application threads were stopped: 0.0032893 seconds
> Total time for which application threads were stopped: 0.0037969 seconds
> Total time for which application threads were stopped: 0.0130588 seconds
> Total time for which application threads were stopped: 0.1230765 seconds
> Total time for which application threads were stopped: 0.0022368 seconds
> Total time for which application threads were stopped: 0.0022032 seconds
> Total time for which application threads were stopped: 0.0505220 seconds
> Total time for which application threads were stopped: 0.0351524 seconds
> Total time for which application threads were stopped: 0.0022816 seconds
> Total time for which application threads were stopped: 0.0292614 seconds
> Total time for which application threads were stopped: 0.0117505 seconds
> Total time for which application threads were stopped: 0.0035653 seconds
> Total time for which application threads were stopped: 0.0388754 seconds
> Total time for which application threads were stopped: 0.0028810 seconds
> Total time for which application threads were stopped: 0.0025892 seconds
> Total time for which application threads were stopped: 0.0028770 seconds
> Total time for which application threads were stopped: 0.0024385 seconds
> Total time for which application threads were stopped: 0.0025007 seconds
> Total time for which application threads were stopped: 0.0024033 seconds
> Total time for which application threads were stopped: 0.0024441 seconds
> Total time for which application threads were stopped: 0.0028249 seconds
> Total time for which application threads were stopped: 0.0026523 seconds
> Total time for which application threads were stopped: 0.0025650 seconds
> Total time for which application threads were stopped: 0.0025241 seconds
> Total time for which application threads were stopped: 0.0026102 seconds
> Total time for which application threads were stopped: 0.0026741 seconds
> Total time for which application threads were stopped: 0.0025973 seconds
> Total time for which application threads were stopped: 0.0027808 seconds
> Total time for which application threads were stopped: 0.0112295 seconds
> Total time for which application threads were stopped: 0.0028798 seconds
> Total time for which application threads were stopped: 0.0026709 seconds
> Total time for which application threads were stopped: 0.0038697 seconds
> Total time for which application threads were stopped: 0.0026591 seconds
> Total time for which application threads were stopped: 0.0025443 seconds
> Total time for which application threads were stopped: 0.0040415 seconds
> Total time for which application threads were stopped: 0.0025476 seconds
> Total time for which application threads were stopped: 0.0025682 seconds
> Total time for which application threads were stopped: 0.0032743 seconds
> Total time for which application threads were stopped: 0.0034255 seconds
> Total time for which application threads were stopped: 0.0034190 seconds
> Total time for which application threads were stopped: 0.0025161 seconds
> Total time for which application threads were stopped: 0.0036486 seconds
> Total time for which application threads were stopped: 0.0034647 seconds
> Total time for which application threads were stopped: 0.0032177 seconds
> Total time for which application threads were stopped: 0.0027416 seconds
> Total time for which application threads were stopped: 0.0034942 seconds
> Total time for which application threads were stopped: 0.0026935 seconds
> Total time for which application threads were stopped: 0.0029138 seconds
> Total time for which application threads were stopped: 0.0026070 seconds
> Total time for which application threads were stopped: 0.0025387 seconds
> Total time for which application threads were stopped: 0.0145426 seconds
> Total time for which application threads were stopped: 0.0031826 seconds
> Total time for which application threads were stopped: 0.0023891 seconds
> Total time for which application threads were stopped: 0.0027578 seconds
> Total time for which application threads were stopped: 0.0742630 seconds
> Total time for which application threads were stopped: 0.0024304 seconds
> Total time for which application threads were stopped: 0.0637979 seconds
> Total time for which application threads were stopped: 0.0198993 seconds
> Total time for which application threads were stopped: 0.0491918 seconds
> Total time for which application threads were stopped: 0.0024178 seconds
> Total time for which application threads were stopped: 0.0098973 seconds
> Total time for which application threads were stopped: 0.0302448 seconds
> Total time for which application threads were stopped: 0.0121276 seconds
> Total time for which application threads were stopped: 0.0025787 seconds
> Total time for which application threads were stopped: 0.0138264 seconds
> Total time for which application threads were stopped: 0.0153000 seconds
> Total time for which application threads were stopped: 0.0027456 seconds
> Total time for which application threads were stopped: 0.0038677 seconds
> Total time for which application threads were stopped: 0.0029987 seconds
> Total time for which application threads were stopped: 0.0054323 seconds
> Total time for which application threads were stopped: 0.0026236 seconds
> Total time for which application threads were stopped: 0.0034756 seconds
> Total time for which application threads were stopped: 0.0028228 seconds
> Total time for which application threads were stopped: 0.0096895 seconds
> Total time for which application threads were stopped: 0.0028705 seconds
> Total time for which application threads were stopped: 0.0038539 seconds
> Total time for which application threads were stopped: 0.0027335 seconds
> Total time for which application threads were stopped: 0.0039392 seconds
> Total time for which application threads were stopped: 0.0030043 seconds
> Total time for which application threads were stopped: 0.0025136 seconds
> Total time for which application threads were stopped: 0.0041170 seconds
> Total time for which application threads were stopped: 0.0134016 seconds
> Total time for which application threads were stopped: 0.0028604 seconds
> Total time for which application threads were stopped: 0.0030666 seconds
> Total time for which application threads were stopped: 0.0092635 seconds
> Total time for which application threads were stopped: 0.0035233 seconds
> Total time for which application threads were stopped: 0.0027291 seconds
> Total time for which application threads were stopped: 0.0026195 seconds
> Total time for which application threads were stopped: 0.0025989 seconds
> Total time for which application threads were stopped: 0.0027949 seconds
> Total time for which application threads were stopped: 0.0035386 seconds
> Total time for which application threads were stopped: 0.0034117 seconds
> Total time for which application threads were stopped: 0.0033919 seconds
> Total time for which application threads were stopped: 0.0024518 seconds
> Total time for which application threads were stopped: 0.0031862 seconds
> Total time for which application threads were stopped: 0.0032185 seconds
> Total time for which application threads were stopped: 0.0028277 seconds
> Total time for which application threads were stopped: 0.0032185 seconds
> Total time for which application threads were stopped: 0.0034893 seconds
> Total time for which application threads were stopped: 0.0027493 seconds
> Total time for which application threads were stopped: 0.0031793 seconds
> Total time for which application threads were stopped: 0.0041045 seconds
> Total time for which application threads were stopped: 0.0025815 seconds
> Total time for which application threads were stopped: 0.0035859 seconds
> Total time for which application threads were stopped: 0.0038022 seconds
> Total time for which application threads were stopped: 0.0029696 seconds
> Total time for which application threads were stopped: 0.0037133 seconds
> Total time for which application threads were stopped: 0.0032796 seconds
> Total time for which application threads were stopped: 0.0030532 seconds
> Total time for which application threads were stopped: 0.0026405 seconds
> Total time for which application threads were stopped: 0.0033176 seconds
> Total time for which application threads were stopped: 0.0032808 seconds
> Total time for which application threads were stopped: 0.0200569 seconds
> Total time for which application threads were stopped: 0.0027396 seconds
> Total time for which application threads were stopped: 0.0037072 seconds
> Total time for which application threads were stopped: 0.0024882 seconds
> Total time for which application threads were stopped: 0.0030096 seconds
> Total time for which application threads were stopped: 0.0024801 seconds
> Total time for which application threads were stopped: 0.0025565 seconds
> Total time for which application threads were stopped: 0.0038931 seconds
> Total time for which application threads were stopped: 0.0030067 seconds
> Total time for which application threads were stopped: 0.0030302 seconds
> Total time for which application threads were stopped: 0.0271912 seconds
> Total time for which application threads were stopped: 0.0026147 seconds
> Heap
> 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
>>
>
>
>
> <wrapperParsed.zip>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.openjdk.java.net/pipermail/hotspot-gc-use/attachments/20150403/068b8d1f/attachment-0001.html>
More information about the hotspot-gc-use
mailing list