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The incremental mode of CMS was implemented for running CMS on machines<br>
with a single hardware thread. The idea was that CMS does work
concurrently<br>
with the application but with a single hardware thread, when CMS ran in<br>
a concurrent phase, it would still be stopping the application (CMS
would<br>
use the single hardware thread and there would be nothing for the
application<br>
to run on). So the incremental mode of CMS does the concurrent phases<br>
in increments and gives up the hardware thread to the application on<br>
a regular basis. On a 4 processor machine I would not recommend the
incremental<br>
mode. If you have not tried the regular CMS (no incremental mode),<br>
I recommend that you try it. Overall it is more efficient.<br>
<br>
On 11/6/10 11:32 PM, Dori Rabin wrote:
<blockquote
cite="mid:AANLkTi=AH1otmk-g+mTy69MGXNE9-G8+ERXT3PuXNSs1@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>Thanks fo your replies...</div>
<div>I am running on jdk1.6.0_04 and OS is Linux 2.4.21-37.ELsmp, I
have 4 processors on the machine</div>
<div>About sharing the log file it might be a little
problematic now so let's discuss it if no other option </div>
<div>I also thought of getting rid of the incremental mode but I am
afraid of the effect of long pauses on our realtime application due to
the stop the world phase of CMS....</div>
<div>I didn't quiet understand what exactly you meant by "scale back
the # parallel threads used by the CMS..." is there a parameter I need
to set for that ? if yes what should be its value ? </div>
<div>Thanks</div>
<div>Dori</div>
<div> </div>
<div> </div>
<div class="gmail_quote">On Thu, Nov 4, 2010 at 6:51 PM, Y. S.
Ramakrishna <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:y.s.ramakrishna@oracle.com">y.s.ramakrishna@oracle.com</a>></span>
wrote:<br>
<blockquote
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;"
class="gmail_quote">Hi Dori --<br>
<br>
What's the version of JDK you are running? Can you share a complete log?<br>
It appears as though the iCMS "auto-pacing" is, for some reason, not<br>
kicking in "soon enough"; one workaround is to use turn off auto-pacing<br>
and use an explicit duty-cycle (which has its own disadvantages).<br>
<br>
I'd suggest filing a bug, and including a complete log file showing<br>
the problem.<br>
<br>
thanks.<br>
-- ramki<br>
<br>
On 11/04/10 06:27, Rabin Dori wrote:<br>
> Hi,<br>
><br>
> Once in a while and for a reason I cannot understand the CMS kicks
up<br>
> too late which causes a promotion failure and full GC that takes
very<br>
> long (more than 2 minutes which causes other problems)…<br>
><br>
> My question is how to tune the gc flags in order to make sure that
the<br>
> concurrent sweep will always occur in parallel (incremental mode)<br>
> without long pause stop the world but also without reaching its
maximum<br>
> capacity ?<br>
><br>
><br>
><br>
> (I know that in my case the *CMSInitiatingOccupancyFraction*=60 is<br>
> ignored because of the CMSIncrementalMode<br>
><br>
> And from looking in the log file we can see that the old generation<br>
> reaches size of 835’959K out of 843’000K at the time the concurrent<br>
> failure (I marked this line in red)<br>
><br>
><br>
><br>
> *_I am running the jvm with the following parameters :_*<br>
><br>
> wrapper.java.additional.4=-XX:NewSize=200m<br>
><br>
> wrapper.java.additional.5=-XX:SurvivorRatio=6<br>
><br>
> wrapper.java.additional.6=-XX:MaxTenuringThreshold=4<br>
><br>
> wrapper.java.additional.7=-XX:+CMSIncrementalMode<br>
><br>
> wrapper.java.additional.8=-XX:+CMSIncrementalPacing<br>
><br>
> wrapper.java.additional.9=-XX:+DisableExplicitGC<br>
><br>
> wrapper.java.additional.10=-XX:+UseConcMarkSweepGC<br>
><br>
> wrapper.java.additional.11=-XX:+CMSClassUnloadingEnabled<br>
><br>
> wrapper.java.additional.12=-XX:+PrintGCDetails<br>
><br>
> wrapper.java.additional.13=-XX:+PrintGCTimeStamps<br>
><br>
> wrapper.java.additional.14=-XX:-TraceClassUnloading<br>
><br>
> wrapper.java.additional.15=-XX:+HeapDumpOnOutOfMemoryError<br>
><br>
> wrapper.java.additional.16=-verbose:gc<br>
><br>
> wrapper.java.additional.17=-XX:CMSInitiatingOccupancyFraction=60<br>
><br>
> wrapper.java.additional.18=-XX:+UseCMSInitiatingOccupancyOnly<br>
><br>
> wrapper.java.additional.19=-XX:+PrintTenuringDistribution<br>
><br>
><br>
><br>
><br>
><br>
> *_Extracts from the log <a class="moz-txt-link-freetext" href="file:_*">file:_*</a><br>
><br>
> INFO | jvm 1 | 2010/11/02 04:54:33 | Desired survivor size
13107200<br>
> bytes, new threshold 4 (max 4)<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:54:33 | - age 1: 544000<br>
> bytes, 544000 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:54:33 | - age 2: 346320<br>
> bytes, 890320 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:54:33 | - age 3: 262800<br>
> bytes, 1153120 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:54:33 | - age 4: 238528<br>
> bytes, 1391648 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:54:33 | :
155621K->2065K(179200K),<br>
> 0.1046330 secs] 988712K->835373K(1022976K) icms_dc=0 ,
0.1047500 secs]<br>
> [Times: user=0.00 sys=0.00, real=0.11 secs]<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:55:54 | 422097.583: [GC
422097.583:<br>
> [ParNew<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:55:54 |<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:55:54 | Desired survivor size
13107200<br>
> bytes, new threshold 4 (max 4)<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:55:54 | - age 1: 577104<br>
> bytes, 577104 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:55:54 | - age 2: 261856<br>
> bytes, 838960 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:55:54 | - age 3: 298832<br>
> bytes, 1137792 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:55:54 | - age 4: 259176<br>
> bytes, 1396968 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:55:54 | :
155664K->2386K(179200K),<br>
> 0.0498010 secs] 988972K->835920K(1022976K) icms_dc=0 ,
0.0499370 secs]<br>
> [Times: user=0.00 sys=0.00, real=0.05 secs]<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:57:27 | 422190.993: [GC
422190.993:<br>
> [ParNew<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:57:28 |<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:57:28 | Desired survivor size
13107200<br>
> bytes, new threshold 4 (max 4)<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:57:28 | - age 1: 676656<br>
> bytes, 676656 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:57:28 | - age 2: 283376<br>
> bytes, 960032 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:57:28 | - age 3: 239472<br>
> bytes, 1199504 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:57:28 | - age 4: 264960<br>
> bytes, 1464464 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:57:28 | :
155986K->1918K(179200K),<br>
> 0.0652010 secs] 989520K->835699K(1022976K) icms_dc=0 ,
0.0653200 secs]<br>
> [Times: user=0.01 sys=0.00, real=0.07 secs]<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:58:54 | 422277.406: [GC
422277.406:<br>
> [ParNew<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:58:54 | Desired survivor size
13107200<br>
> bytes, new threshold 4 (max 4)<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:58:54 | - age 1: 615944<br>
> bytes, 615944 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:58:54 | - age 2: 334120<br>
> bytes, 950064 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:58:54 | - age 3: 276736<br>
> bytes, 1226800 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:58:54 | - age 4: 236424<br>
> bytes, 1463224 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 04:58:54 | :
155518K->1928K(179200K),<br>
> 0.0378730 secs] 989299K->835959K(1022976K) icms_dc=0 ,
0.0379920 secs]<br>
> [Times: user=0.00 sys=0.00, real=0.04 secs]<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:00:23 | 422366.439: [GC
422366.439:<br>
> [ParNew<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:00:23 | (promotion failed)<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:00:23 | Desired survivor size
13107200<br>
> bytes, new threshold 4 (max 4)<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:00:23 | - age 1: 574000<br>
> bytes, 574000 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:00:23 | - age 2: 315432<br>
> bytes, 889432 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:00:23 | - age 3: 281216<br>
> bytes, 1170648 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:00:23 | - age 4: 271776<br>
> bytes, 1442424 total<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:00:23 | :
155528K->155689K(179200K),<br>
> 0.1007840 secs]422366.540: [CMS<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:01:46 | [Unloading class<br>
> sun.reflect.GeneratedMethodAccessor121]<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:01:46 | [Unloading class<br>
> sun.reflect.GeneratedMethodAccessor119]<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:01:46 | [Unloading class<br>
> sun.reflect.GeneratedMethodAccessor124]<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:01:46 | [Unloading class<br>
> sun.reflect.GeneratedMethodAccessor123]<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:01:46 | [Unloading class<br>
> sun.reflect.GeneratedMethodAccessor120]<br>
><br>
> INFO | jvm 1 | 2010/11/02 05:01:46 | [Unloading class<br>
> sun.reflect.GeneratedMethodAccessor122]<br>
><br>
> ERROR | wrapper | 2010/11/02 05:02:37 | JVM appears hung: Timed
out<br>
> waiting for signal from JVM.<br>
><br>
><br>
><br>
><br>
><br>
> *Dori Rabin*<br>
><br>
> *<a class="moz-txt-link-freetext" href="cid:image001.gif@01CB69E7.E5E45760*">cid:image001.gif@01CB69E7.E5E45760*</a><br>
><br>
><br>
><br>
> *<a class="moz-txt-link-freetext" href="cid:image002.jpg@01CB69E7.E5E45760*">cid:image002.jpg@01CB69E7.E5E45760*</a><br>
><br>
> T. +972-3-123-4567 F. +972-3- 766-3559 M. +972-54- 4232-706<br>
><br>
> Email: mailto:<a moz-do-not-send="true" href="mailto:Dori">Dori</a>
<mailto:<a moz-do-not-send="true" href="mailto:your-email-address">your-email-address</a>>.<a
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><br>
><br>
><br>
><br>
><br>
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</blockquote>
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