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On 4/14/10 1:29 PM, Shaun Hennessy wrote:
<blockquote cite="mid:4BC62595.2000002@alcatel-lucent.com" type="cite">
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...<tt><br>
</tt><br>
<blockquote cite="mid:148A7A57-B616-4CA4-9571-0F0216B0F650@oracle.com"
type="cite">
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<blockquote cite="mid:4BB20B1C.4020608@alcatel-lucent.com"
type="cite"><tt> <br>
<br>
<br>
promotion failed, and full GC<br>
50786.124: [GC 50786.124: [ParNew: 4606713K->338518K(5017600K),
0.0961884 secs] 12303455K->8081859K(13619200K), 0.0963907 secs]
[Times: user=0.91 sys=0.01, real=0.10 secs]<br>
50787.373: [GC 50787.373: [ParNew: 4639318K->272229K(5017600K),
0.0749353 secs] 12382659K->8053730K(13619200K), 0.0751408 secs]
[Times: user=0.75 sys=0.00, real=0.08 secs]<br>
50788.483: [GC 50788.483: [ParNew: 4573029K->393397K(5017600K),
0.0837182 secs] 12354530K->8185595K(13619200K), 0.0839321 secs]
[Times: user=1.03 sys=0.00, real=0.08 secs]<br>
50789.590: [GC 50789.590: [ParNew (promotion failed):
4694264K->4612345K(5017600K), 1.5974678 secs]
12486461K->12447305K(13619200K), 1.5976765 secs] [Times : user=2.38
sys=0.20, real=1.60 secs]<br>
GC locker: Trying a full collection because scavenge failed<br>
50791.188: [Full GC 50791.188: [CMS: 7834959K->1227325K(8601600K),
6.7102106 secs] 12447305K->1227325K(13619200K), [CMS Perm :
670478K->670478K(819200K)], 6.7103417 secs] [Times: user=6.71
sys=0.00, real=6.71 secs]<br>
50798.982: [GC 50798.982: [ParNew: 4300800K->217359K(5017600K),
0.0364557 secs] 5528125K->1444685K(13619200K), 0.0366630 secs]
[Times: user=0.44 sys=0.00, real=0.04 secs]<br>
50800.246: [GC 50800.246: [ParNew: 4518167K->198753K(5017600K),
0.0368620 secs] 5745493K->1426078K(13619200K), 0.0370604 secs]
[Times: user=0.46 sys=0.01, real=0.04 secs]<br>
9) Probably once I understand what the scavenge is doing will help me
understand this case, but logic seems<br>
simply enough - fullgc on promotionfailure&scavenge failed.<br>
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Yes, full STW compaction.</div>
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3) So in the prevous case (promotion failed) you said it was "full STW
compaction of the entire heap is done" and <br>
here in the (promotion failed; GC locker; Full GC) also "full STW
compaction" --- what is the difference between<br>
the 2 scenarios (ie cause and effect)? From below your "<i>The "GC
locker" message says that after a JNI critical <br>
section was exited the GC wanted to do a scavenge but did not think
there was enough room in the old gen so it <br>
does a full STW compaction." -- </i>so the cause of the difference
between the 2 cases is simply the fact the tenured<br>
generation was more full in this latest case? So in terms of
effect -- is anything different actually<br>
being done regarding the between the 2 cases or is just the log
messages being displayed are different - but they<br>
are the exact same type of GC?<br>
<br>
</blockquote>
The collections are the same (both full STW compactions). The only
difference are<br>
the circumstances under which the GC were done. JNI critical sections
can<br>
temporarily delay a GC and whenthe critical section is exited the
delayed<br>
GC happens. That's about all I know about that.<br>
<blockquote cite="mid:4BC62595.2000002@alcatel-lucent.com" type="cite"><br>
4) Forgetting these specific examples, if we are having
frequent/troublesome promotion failures <br>
is there anything beyond <br>
</blockquote>
<br>
Those are the usual remedies. I suppose you could also try to reduce
the<br>
amount of allocations you do.<br>
<br>
<blockquote cite="mid:4BC62595.2000002@alcatel-lucent.com" type="cite"><br>
a) Try 6u20<br>
b) Try a lower InitiatingOccupancy <br>
c) Try a smaller Eden Gen & bigger Tenured / or simply bigger Heap<br>
- Does the use of Survivor Space vs not using Survivor make it more or
less likely to have promotion failures?<br>
</blockquote>
Having survivor spaces are better in general.<br>
<br>
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