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Hi Thomas,<br>
<br>
A very late reply. I happened to find this in my inbox and have some
comments.<br>
<br>
<div class="moz-cite-prefix">On 2014-08-29 14:15, Thomas Viessmann
wrote:<br>
</div>
<blockquote cite="mid:54006ED6.7050006@oracle.com" type="cite">
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Hi all,<br>
<br>
<br>
I suspect a bug in G1 logging. Before I file a (possibly
incorrect) bug I would like to ask here.<br>
Is my understanding correct that the stw evacuation phase starts
at <tt><font color="#ff0000"><b>48448.931</b></font></tt> and
ends at <tt><b><font color="#ff0000">48454</font></b><b><font
color="#ff0000">.034</font></b></tt> ?<br>
This would mean a stop time of 5.103 s, which is clearly a
mismatch to the reported <b><small><font color="#ff0000">9.3426141</font></small></b>
s<br>
If the stw phase in fact started at a later time e.g. at <tt><b><font
color="#ff0000">48449.288 </font></b></tt>then the stop
pause would have been even shorter.<br>
<br>
In addition I do not understand how all the relatively short
evacuation phases sum up to several seconds.<br>
If I add all the MAX values <b><font color="#00cccc"><tt>69.1 + </tt><tt>22.2</tt>
+ <tt>45</tt><tt> + 150.8 + </tt><tt>0.1</tt> + <tt>155.1</tt>
+ <tt>0.9 + </tt><tt>0.5</tt></font></b><small> <b><font
color="#00cccc">= 443.7</font></b><b><font color="#00cccc">ms</font></b></small><br>
<br>
<br>
<br>
<tt><br>
</tt><tt>48443.380: Total time for which application threads were
stopped: 0.0084701 seconds</tt><tt><br>
</tt><tt><font color="#ff0000"><b>48448.931</b></font>: [GC pause
(mixed) 48448.931: [G1Ergonomics (CSet Construction) start
choosing CSet, _pending_cards: 89458, predicted base time: 73.58
ms, remaining time: 176.42 ms, target pause time: 250.00 ms]</tt><tt><br>
</tt><tt> 48448.931: [G1Ergonomics (CSet Construction) add young
regions to CSet, eden: 33 regions, survivors: 5 regions,
predicted young region time: 35.73 ms]</tt><tt><br>
</tt><tt> 48448.933: [G1Ergonomics (CSet Construction) finish
adding old regions to CSet, reason: reclaimable percentage not
over threshold, old: 19 regions, max: 77 regions, reclaimable:
2570649712 bytes (9.98 %), threshold: 10.00 %]</tt><tt><br>
</tt><tt> 48448.933: [G1Ergonomics (CSet Construction) added
expensive regions to CSet, reason: old CSet region num not
reached min, old: 19 regions, expensive: 7 regions, min: 26
regions, remaining time: 0.00 ms]</tt><tt><br>
</tt><tt> 48448.933: [G1Ergonomics (CSet Construction) finish
choosing CSet, eden: 33 regions, survivors: 5 regions, old: 19
regions, predicted pause time: 340.58 ms, target pause time:
250.00 ms]</tt><tt><br>
</tt><tt>48449.252: [SoftReference, 962 refs, 0.0064679
secs]48449.259: [WeakReference, 7411 refs, 0.0027722
secs]48449.261: [FinalReference, 272 refs, 0.0022754
secs]48449.264: [PhantomReference, 6 refs, 0.0024348
secs]48449.266: [JNI Weak Reference, 0.0000337 secs] 48449.288:
[G1Ergonomics (Concurrent Cycles) do not request concurrent
cycle initiation, reason: still doing mixed collections,
occupancy: 14898167808 bytes, allocation request: 0 bytes,
threshold: 11596411665 bytes (45.00 %), source: end of GC]</tt><tt><br>
</tt><tt> <b><font color="#ff0000">48449.288</font></b>:
[G1Ergonomics (Mixed GCs) do not continue mixed GCs, reason:
reclaimable percentage not over threshold, candidate old
regions: 156 regions, reclaimable: 2570649712 bytes (9.98 %),
threshold: 10.00 %]</tt><tt><br>
</tt><tt>, 0.3573636 secs]</tt><tt><br>
</tt><tt> [Parallel Time: 314.9 ms, GC Workers: 40]</tt><tt><br>
</tt><tt> [GC Worker Start (ms): Min: 48448933.6, Avg:
48448934.2, Max: 48448934.7, Diff: 1.1]</tt><tt><br>
</tt><tt> [Ext Root Scanning (ms): Min: 15.1, Avg: 17.7, Max:
<b><font color="#00cccc">69.1</font></b>, Diff: 54.0, Sum:
708.0]</tt><tt><br>
</tt><tt> [Update RS (ms): Min: 0.0, Avg: 14.5, Max: <b><font
color="#00cccc">22.2</font></b>, Diff: 22.2, Sum: 580.3]</tt><tt><br>
</tt><tt> [Processed Buffers: Min: 0, Avg: 22.0, Max: <b><font
color="#00cccc">45</font></b>, Diff: 45, Sum: 879]</tt><tt><br>
</tt><tt> [Scan RS (ms): Min: 88.7, Avg: 142.6, Max: <b><font
color="#00cccc">150.8</font></b>, Diff: 62.1, Sum: 5705.2]</tt><tt><br>
</tt><tt> [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max:
<b><font color="#00cccc">0.1</font></b>, Diff: 0.1, Sum: 0.1]</tt><tt><br>
</tt><tt> [Object Copy (ms): Min: 131.4, Avg: 138.2, Max: <b><font
color="#00cccc">155.1</font></b>, Diff: 23.8, Sum: 5526.6]</tt><tt><br>
</tt><tt> [Termination (ms): Min: 0.0, Avg: 0.7, Max: <b><font
color="#00cccc">0.9</font></b>, Diff: 0.9, Sum: 27.2]</tt><tt><br>
</tt><tt> [GC Worker Other (ms): Min: 0.0, Avg: 0.3, Max: <b><font
color="#00cccc">0.5</font></b>, Diff: 0.5, Sum: 10.0]</tt><tt><br>
</tt><tt> [GC Worker Total (ms): Min: 313.2, Avg: 313.9, Max:
<b><font color="#00cccc">314.7</font></b>, Diff: 1.5, Sum:
12557.5]</tt><tt><br>
</tt><tt> [GC Worker End (ms): Min: 48449247.9, Avg:
48449248.1, Max: 48449248.4, Diff: 0.5]</tt><tt><br>
</tt><tt> [Code Root Fixup: 2.2 ms]</tt><tt><br>
</tt><tt> [Code Root Migration: 0.2 ms]</tt><tt><br>
</tt><tt> [Clear CT: 2.0 ms]</tt><tt><br>
</tt><tt> [Other: 38.2 ms]</tt><tt><br>
</tt><tt> [Choose CSet: 1.7 ms]</tt><tt><br>
</tt><tt> [Ref Proc: 15.6 ms]</tt><tt><br>
</tt><tt> [Ref Enq: 1.2 ms]</tt><tt><br>
</tt><tt> [Free CSet: 2.4 ms]</tt><tt><br>
</tt><tt> [Eden: 1056.0M(1056.0M)->0.0B(1088.0M) Survivors:
160.0M->128.0M Heap: 14.5G(24.0G)->13.9G(24.0G)]</tt><tt><br>
</tt><tt> [Times: user=12.45 sys=0.03, real=0.36 secs] </tt><tt><br>
</tt><tt><b><font color="#ff0000">48454</font></b><b><font
color="#ff0000">.034</font></b>: Total time for which
application threads were stopped: <b><font color="#ff0000">9.3426141</font></b>
seconds</tt><tt><br>
</tt><br>
For completeness; here are the cmd line options:<br>
<br>
<br>
/usr/jdk/instances/jdk1.7.0/bin/sparcv9/java -Xms24g -Xmx24g
-server -XX:StringTableSize=27001 -XX:PermSize=512m
-XX:MaxPermSize=512m -Xss512k <br>
-XX:+UseG1GC -XX:SoftRefLRUPolicyMSPerMB=500 -XX:+PrintGCDetails
-XX:+PrintGCTimeStamps
-Xloggc:/var/cacao/instances/oem-ec/logs/gc.log
-XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10
-XX:GCLogFileSize=10m -XX:+PrintGCApplicationStoppedTime
-XX:MaxGCPauseMillis=250-XX:InitiatingHeapOccupancyPercent=45
-XX:+ParallelRefProcEnabled -XX:ParallelGCThreads=40
-XX:+PrintAdaptiveSizePolicy -XX:+PrintSafepointStatistics
-XX:+PrintReferenceGC -XX:G1HeapRegionSize=32m
-XX:HeapBaseMinAddress=2G <br>
</blockquote>
<br>
<br>
The GC starts at 48448.931 and reports that it lasts for 0.36
seconds, so it should have ended at 48449.291. The last log line
that states that the threads were stopped for 9 seconds is from the
PrintGCApplicationStoppedTime flag, which logs how long the
safepoint was. i.e. how long the Java threads where stopped.<br>
<br>
This means that the safepoint lasted for 9 seconds but the GC only
lasted for 0.36 seconds. So the rest of the time must be attributed
to stopping and starting the Java threads. The safepoint was started
at 48444.691 (48454.034 - 9.3426141), which means that it took 4.240
seconds (48448.931 - 48444.691) to stop all Java threads and 4.743
seconds (9.3426141 - 4.240 - 0.36) to start them again. <br>
<br>
I don't have a good explanation for why it takes so long to stop and
start the threads. Are there many Java threads in the application?
Are there many other processes running that could cause the Java
threads to be scheduled out?<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<blockquote cite="mid:54006ED6.7050006@oracle.com" type="cite"> <br>
<br>
<br>
Thanks and Regards<br>
<br>
Thomas <br>
<br>
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