Pauses with the CMS

mrk mrk at autocom.dk
Thu Oct 28 01:48:17 PDT 2010


Hi

Isn't u22 good enough? I'm not too keen on using PreRelease software.

med venlig hilsen / Best regards,
Morten Knudsen

"Y. Srinivas Ramakrishna" 
<y.s.ramakrishna at oracle.com> skrev i 
meddelelsen news:4CC92E90.8090301 at oracle.com...
> Hi Morten --
>
> On 10/28/2010 12:40 AM, mrk wrote:
>> Hi Ramki
>>
>> Thanks for your answer. I have read the CR description. It mentions NIO. 
>> We do not use the NIO
>> connector in Tomcat. Could the CR be affecting us anyway?
>
> It need not be NIO, but it could be something else perhaps not directly 
> used
> by you but indirectly through the core JDK libraries that makes use of
> JNI Critical Sections (NIO used to use that mechanism until recently
> but no longer does).
>
> I think it's worth a try, since the symptoms you describe are very similar 
> to
> 6919638. Try the workaround or 6u23/JDK 7 latest and, if it doesn't work,
> closer investigation will be warranted, at which time you will want to
> open a ticket via your support channels and/or provide a test case
> exhibiting the problem.
>
> best regards.
> -- ramki
>
>>
>> med venlig hilsen / Best regards,
>> Morten Knudsen
>>
>> "Y. S. Ramakrishna" 
>> <y.s.ramakrishna at oracle.com> skrev i 
>> meddelelsen
>> news:4CC84F4E.2080302 at oracle.com...
>>> There were two related CR's which may be affecting you:
>>>
>>> (1) 6692906 CMS: parallel concurrent marking may be prone to hanging or 
>>> stalling mutators for
>>> periods of time
>>> I do not think this is affecting you.
>>>
>>> (2) 6919638 CMS: ExplicitGCInvokesConcurrent misinteracts with gc locker
>>>
>>> I suspect it could be this latter CR that's affecting you. If so, it's
>>> fixed in 6u22 and in 6u23 (and in 7 since 7bb95), so you might want to
>>> try those. There's also a workaround documented in the CR.
>>>
>>> -- ramki
>>>
>>>
>>> On 10/27/10 01:50, mrk wrote:
>>>> Hi All
>>>>
>>>> Hi
>>>>
>>>> We have made a webapp running in JBoss 4.2.3 on RedHat Linux 5.2 on a 
>>>> 12 core IBM machine. Lately
>>>> we have seen long response times, which seems to be caused be GC 
>>>> activities. The pattern is more
>>>> or less as follows:
>>>> All requests seem to come at normal rate, but no bytes are sent until 
>>>> suddenly all responses are
>>>> "flushed".
>>>> At same time the gc.log has this pattern:
>>>>
>>>> // Here the unresponsiveness starts
>>>> 36788.309: [GC [1 CMS-initial-mark: 1919297K(4456448K)] 
>>>> 1969797K(5111808K), 0.1473460 secs]
>>>> [Times: user=0.15 sys=0.00, real=0.15 secs]
>>>> Total time for which application threads were stopped: 0.1530790 
>>>> seconds
>>>> 36788.457: [CMS-concurrent-mark-start]
>>>> 36793.886: [CMS-concurrent-mark: 5.429/5.429 secs] (CMS-concurrent-mark 
>>>> yielded 46 times)
>>>> [Times: user=6.69 sys=0.07, real=5.43 secs]
>>>> 36793.886: [CMS-concurrent-preclean-start]
>>>> (cardTable: 15956 cards, re-scanned 15956 cards, 1 iterations)
>>>> 36793.988: [CMS-concurrent-preclean: 0.089/0.101 secs] 
>>>> (CMS-concurrent-preclean yielded 9 times)
>>>> [Times: user=0.12 sys=0.01, real=0.10 secs]
>>>> 36793.988: [CMS-concurrent-abortable-preclean-start]
>>>> (cardTable: 75 cards, re-scanned 75 cards, 1 iterations)
>>>> Application time: 5.6923460 seconds
>>>> Total time for which application threads were stopped: 0.0170000 
>>>> seconds
>>>> (cardTable: 96 cards, re-scanned 96 cards, 1 iterations)
>>>> (cardTable: 207 cards, re-scanned 207 cards, 1 iterations)
>>>> (cardTable: 45 cards, re-scanned 45 cards, 1 iterations)
>>>> (cardTable: 157 cards, re-scanned 157 cards, 1 iterations)
>>>> (cardTable: 88 cards, re-scanned 88 cards, 1 iterations)
>>>> (cardTable: 213 cards, re-scanned 213 cards, 1 iterations)
>>>> (cardTable: 84 cards, re-scanned 84 cards, 1 iterations)
>>>> (cardTable: 143 cards, re-scanned 143 cards, 1 iterations)
>>>> (cardTable: 40 cards, re-scanned 40 cards, 1 iterations)
>>>> (cardTable: 109 cards, re-scanned 109 cards, 1 iterations)
>>>> (cardTable: 77 cards, re-scanned 77 cards, 1 iterations)
>>>> (cardTable: 156 cards, re-scanned 156 cards, 1 iterations)
>>>> (cardTable: 132 cards, re-scanned 132 cards, 1 iterations)
>>>> (cardTable: 119 cards, re-scanned 119 cards, 1 iterations)
>>>> (cardTable: 115 cards, re-scanned 115 cards, 1 iterations)
>>>> (cardTable: 195 cards, re-scanned 195 cards, 1 iterations)
>>>> (cardTable: 163 cards, re-scanned 163 cards, 1 iterations)
>>>> (cardTable: 166 cards, re-scanned 166 cards, 1 iterations)
>>>> (cardTable: 149 cards, re-scanned 149 cards, 1 iterations)
>>>> (cardTable: 218 cards, re-scanned 218 cards, 1 iterations)
>>>> (cardTable: 46 cards, re-scanned 46 cards, 1 iterations)
>>>> (cardTable: 57 cards, re-scanned 57 cards, 1 iterations)
>>>> (cardTable: 213 cards, re-scanned 213 cards, 1 iterations)
>>>> (cardTable: 189 cards, re-scanned 189 cards, 1 iterations)
>>>> (cardTable: 104 cards, re-scanned 104 cards, 1 iterations)
>>>> (cardTable: 60 cards, re-scanned 60 cards, 1 iterations)
>>>> (cardTable: 368 cards, re-scanned 368 cards, 1 iterations)
>>>> (cardTable: 118 cards, re-scanned 118 cards, 1 iterations)
>>>> (cardTable: 129 cards, re-scanned 129 cards, 1 iterations)
>>>> (cardTable: 291 cards, re-scanned 291 cards, 1 iterations)
>>>> (cardTable: 105 cards, re-scanned 105 cards, 1 iterations)
>>>> (cardTable: 63 cards, re-scanned 63 cards, 1 iterations)
>>>> (cardTable: 73 cards, re-scanned 73 cards, 1 iterations)
>>>> (cardTable: 165 cards, re-scanned 165 cards, 1 iterations)
>>>> (cardTable: 69 cards, re-scanned 69 cards, 1 iterations)
>>>> (cardTable: 157 cards, re-scanned 157 cards, 1 iterations)
>>>> CMS: abort preclean due to time [37 iterations, 13 waits, 4954 cards)] 
>>>> 36799.161:
>>>> [CMS-concurrent-abortable-preclean: 2.965/5.173 secs] 
>>>> (CMS-concurrent-abortable-preclean yielded
>>>> 166 times)
>>>> [Times: user=5.12 sys=0.10, real=5.17 secs]
>>>> Application time: 4.9945030 seconds
>>>> 36799.172: [GC[YG occupancy: 572074 K (655360 K)]36799.172: [GC 
>>>> 36799.173: [ParNew
>>>> Desired survivor size 67108864 bytes, new threshold 2 (max 15)
>>>> - age 1: 59654872 bytes, 59654872 total
>>>> - age 2: 26827232 bytes, 86482104 total
>>>> - age 3: 2613360 bytes, 89095464 total
>>>> - age 4: 929600 bytes, 90025064 total
>>>> - age 5: 893176 bytes, 90918240 total
>>>> - age 6: 795736 bytes, 91713976 total
>>>> - age 7: 809240 bytes, 92523216 total
>>>> - age 8: 936216 bytes, 93459432 total
>>>> - age 9: 971376 bytes, 94430808 total
>>>> - age 10: 624472 bytes, 95055280 total
>>>> - age 11: 883616 bytes, 95938896 total
>>>> - age 12: 817296 bytes, 96756192 total
>>>> - age 13: 977992 bytes, 97734184 total
>>>> - age 14: 733816 bytes, 98468000 total
>>>> - age 15: 654744 bytes, 99122744 total
>>>> : 572074K->110988K(655360K), 0.1855140 secs] 
>>>> 2491372K->2031059K(5111808K) icms_dc=0 , 0.1866380
>>>> secs] [Times: user=0.72 sys=0.00, real=0.19 secs]
>>>> 36799.359: [Rescan (parallel) (Survivor:12chunks) Finished young gen 
>>>> rescan work in 3th thread:
>>>> 0.032 sec
>>>> Finished young gen rescan work in 2th thread: 0.035 sec
>>>> Finished young gen rescan work in 0th thread: 0.035 sec
>>>> Finished young gen rescan work in 1th thread: 0.035 sec
>>>> Finished remaining root rescan work in 1th thread: 0.030 sec
>>>> Finished remaining root rescan work in 3th thread: 0.033 sec
>>>> Finished remaining root rescan work in 2th thread: 0.032 sec
>>>> Finished remaining root rescan work in 0th thread: 0.042 sec
>>>> Finished dirty card rescan work in 2th thread: 0.029 sec
>>>> Finished dirty card rescan work in 3th thread: 0.031 sec
>>>> Finished dirty card rescan work in 0th thread: 0.019 sec
>>>> Finished dirty card rescan work in 1th thread: 0.031 sec
>>>> Finished work stealing in 3th thread: 0.000 sec
>>>> Finished work stealing in 0th thread: 0.000 sec
>>>> Finished work stealing in 2th thread: 0.000 sec
>>>> Finished work stealing in 1th thread: 0.000 sec
>>>> , 0.0959640 secs]36799.455: [weak refs processing, 0.0121220 secs] [1 
>>>> CMS-remark:
>>>> 1920070K(4456448K)] 2031059K(5111808K), 0.2952350 secs] [Times: 
>>>> user=1.11 sys=0.00, real=0.30 secs]
>>>> Total time for which application threads were stopped: 0.3066430 
>>>> seconds
>>>> 36799.468: [CMS-concurrent-sweep-start]
>>>> 36805.824: [CMS-concurrent-sweep: 6.355/6.356 secs] 
>>>> (CMS-concurrent-sweep yielded 515 times)
>>>> [Times: user=8.76 sys=0.24, real=6.35 secs]
>>>> 36805.824: [CMS-concurrent-reset-start]
>>>> 36805.903: [CMS-concurrent-reset: 0.079/0.079 secs] 
>>>> (CMS-concurrent-reset yielded 0 times)
>>>> [Times: user=0.64 sys=0.01, real=0.07 secs]
>>>> Application time: 6.5590510 seconds
>>>> // About here the server starts sending out responses
>>>> 36806.044: [GC 36806.045: [ParNew
>>>> Desired survivor size 67108864 bytes, new threshold 2 (max 15)
>>>> - age 1: 55456640 bytes, 55456640 total
>>>> - age 2: 54278984 bytes, 109735624 total
>>>> : 635276K->131072K(655360K), 0.3230430 secs] 
>>>> 2554507K->2089990K(5111808K) icms_dc=0 , 0.3242750
>>>> secs] [Times: user=1.02 sys=0.02, real=0.33 secs]
>>>> Total time for which application threads were stopped: 0.3422430 
>>>> seconds
>>>> Application time: 0.7628480 seconds
>>>>
>>>> We have tried various GC setups, but we always end up more or less like 
>>>> this.
>>>> Our current parameters:
>>>> -Xms4096m -Xmx5120m -XX:MaxPermSize=384m
>>>> -XX:+UseConcMarkSweepGC -XX:+ExplicitGCInvokesConcurrent
>>>> -XX:+PrintClassHistogram -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCApplicationStoppedTime
>>>> -XX:+PrintGCDetails
>>>> -XX:ReservedCodeCacheSize=64m -XX:NewSize=768m -XX:SurvivorRatio=4
>>>> -XX:+CMSParallelRemarkEnabled -XX:+CMSScavengeBeforeRemark -XX:+CMSIncrementalMode
>>>> -XX:+CMSIncrementalPacing -XX:CMSIncrementalDutyCycleMin=0 -XX:CMSIncrementalDutyCycle=10
>>>> -XX:+UseTLAB -XX:ParallelGCThreads=4
>>>> -XX:+UseParNewGC -XX:MaxGCPauseMillis=1000 -XX:GCTimeRatio=10 -XX:+CMSPermGenSweepingEnabled
>>>> -XX:+PrintCMSInitiationStatistics -XX:PrintCMSStatistics=1 -XX:+PrintGCTaskTimeStamps
>>>> -XX:+PrintGCTimeStamps
>>>> -verbose:gc -XX:+TraceClassLoading -XX:+TraceClassUnloading
>>>> -XX:+PrintTenuringDistribution
>>>>
>>>> How can we avoid the unresponsiveness?
>>>>
>>>> We have tried with both JDK 1.6.0_06 and JDK 1.6.0_021.
>>>>
>>>> It seems that the problem have a lot in common with:
>>>> http://old.nabble.com/long-unaccounted-pause-during-concurrent-mark-phase-of-ParNew-cycle-to27459365.html#a27463304
>>>> But setting -XX:-CMSConcurrentMTEnabled does not seem to help?
>>>>
>>>> med venlig hilsen / Best regards,
>>>> Morten Knudsen
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>
>>
>
> 




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