G1gc compaction algorithm

[Yu Zhang]

Martin,

Based on this one, can you do one with -XX:G1MaxNewSizePercent=30 
-XX:InitiatingHeapOccupancyPercent=20 added?

The reason for G1MaxNewSizePercent(default=60) is to set an upper limit 
to Eden size.  It seems the Eden size grows to 17g before Full gc, then 
a bunch of humongous allocation happened, and there is not enough old gen.

The following log entry seems not right: The Eden Size is over 60% of 
the heap.
"2014-08-11T11:13:05.487+0300: 193238.308: [GC pause (young) 
(initial-mark) 193238.308: [G1Ergonomics (CSet Construction) start 
choosing CSet, _pending_cards: 769041, predicted base time: 673.25 ms, 
remaining time: 326.75 ms, target pause time: 1000.00 ms] 193238.308: 
[G1Ergonomics (CSet Construction) add young regions to CSet, eden: 1 
regions, survivors: 21 regions, predicted young region time: 145.63 ms] 
193238.308: [G1Ergonomics (CSet Construction) finish choosing CSet, 
eden: 1 regions, survivors: 21 regions, old: 0 regions, predicted pause 
time: 818.88 ms, target pause time: 1000.00 ms], 0.7559550 secs]   
[Parallel Time: 563.9 ms, GC Workers: 13]      [GC Worker Start (ms): 
Min: 193238308.1, Avg: 193238318.0, Max: 193238347.6, Diff: 39.5]      
[Ext Root Scanning (ms): Min: 0.0, Avg: 13.0, Max: 35.8, Diff: 35.8, 
Sum: 168.4]      [Update RS (ms): Min: 399.2, Avg: 416.8, Max: 442.8, 
Diff: 43.6, Sum: 5418.0]         [Processed Buffers: Min: 162, Avg: 
232.0, Max: 326, Diff: 164, Sum: 3016] [Scan RS (ms): Min: 0.0, Avg: 
0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]      [Object Copy (ms): Min: 79.9, 
Avg: 104.8, Max: 152.4, Diff: 72.5, Sum: 1363.0]      [Termination (ms): 
Min: 0.0, Avg: 19.1, Max: 27.3, Diff: 27.3, Sum: 248.9]      [GC Worker 
Other (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.3]      [GC 
Worker Total (ms): Min: 524.1, Avg: 553.8, Max: 563.7, Diff: 39.6, Sum: 
7198.8]      [GC Worker End (ms): Min: 193238871.7, Avg: 193238871.8, 
Max: 193238871.8, Diff: 0.1]
    [Code Root Fixup: 0.0 ms]
    [Clear CT: 0.3 ms]
    [Other: 191.7 ms]
       [Choose CSet: 0.0 ms]      [Ref Proc: 190.1 ms] [Ref Enq: 0.3 
ms]      [Free CSet: 0.2 ms]
    [Eden: 16.0M(2464.0M)->0.0B(22.9G) Survivors: 336.0M->240.0M Heap: 
14.1G(28.7G)->14.1G(28.7G)]
  [Times: user=8.45 sys=0.04, real=0.75 secs]"

The reason for increasing InitiatingHeapOccupancyPercent to 20 from 10 
is we are wasting some concurrent cycles.

We will see how this goes.  We might increase G1ReservePercent to handle 
this kind of allocation if it is not enough.

Thanks,
Jenny

Thanks,
Jenny

On 8/11/2014 10:46 AM, Martin Makundi wrote:
> Hi!
>
> Here is our latest log with one Full GC @ 2014-08-11T11:20:02 which is 
> caused by heap full and allocation request: 144 bytes.
>
> http://81.22.250.165/log/gc-16m-2014-08-11.log
>
> Any ideas how to mitigate this kind of situation? The Full GC makes 
> quite a difference to the situation but causes a painful pause also.
>
> **
> Martin

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