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From rohit bhatia <rohit2...@gmail.com>
Subject Re: GC freeze just after repair session
Date Fri, 06 Jul 2012 05:57:58 GMT
@ravi, u can increase young gen size, keep a high tenuring rate or
increase survivor ratio..


On Fri, Jul 6, 2012 at 4:03 AM, aaron morton <aaron@thelastpickle.com> wrote:
> Ideally we would like to collect maximum garbage from ParNew itself, during
> compactions. What are the steps to take towards to achieving this?
>
> I'm not sure what you are asking.
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 5/07/2012, at 6:56 PM, Ravikumar Govindarajan wrote:
>
> We have modified maxTenuringThreshold from 1 to 5. May be it is causing
> problems. Will change it back to 1 and see how the system is.
>
> concurrent_compactors=8. We will reduce this, as anyway our system won't be
> able to handle this number of compactions at the same time. Think it will
> ease GC also to some extent.
>
> Ideally we would like to collect maximum garbage from ParNew itself, during
> compactions. What are the steps to take towards to achieving this?
>
> On Wed, Jul 4, 2012 at 4:07 PM, aaron morton <aaron@thelastpickle.com>
> wrote:
>>
>> It *may* have been compaction from the repair, but it's not a big CF.
>>
>> I would look at the logs to see how much data was transferred to the node.
>> Was their a compaction going on while the GC storm was happening ? Do you
>> have a lot of secondary indexes ?
>>
>> If you think it correlated to compaction you can try reducing the
>> concurrent_compactors
>>
>> Cheers
>>
>> -----------------
>> Aaron Morton
>> Freelance Developer
>> @aaronmorton
>> http://www.thelastpickle.com
>>
>> On 3/07/2012, at 6:33 PM, Ravikumar Govindarajan wrote:
>>
>> Recently, we faced a severe freeze [around 30-40 mins] on one of our
>> servers. There were many mutations/reads dropped. The issue happened just
>> after a routine nodetool repair for the below CF completed [1.0.7, NTS,
>> DC1:3,DC2:2]
>>
>> Column Family: MsgIrtConv
>> SSTable count: 12
>> Space used (live): 17426379140
>> Space used (total): 17426379140
>> Number of Keys (estimate): 122624
>> Memtable Columns Count: 31180
>> Memtable Data Size: 81950175
>> Memtable Switch Count: 31
>> Read Count: 8074156
>> Read Latency: 15.743 ms.
>> Write Count: 2172404
>> Write Latency: 0.037 ms.
>> Pending Tasks: 0
>> Bloom Filter False Postives: 1258
>> Bloom Filter False Ratio: 0.03598
>> Bloom Filter Space Used: 498672
>> Key cache capacity: 200000
>> Key cache size: 200000
>> Key cache hit rate: 0.9965579513062582
>> Row cache: disabled
>> Compacted row minimum size: 51
>> Compacted row maximum size: 89970660
>> Compacted row mean size: 226626
>>
>>
>> Our heap config is as follows
>>
>> -Xms8G -Xmx8G -Xmn800M -XX:+HeapDumpOnOutOfMemoryError -XX:+UseParNewGC
>> -XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled -XX:SurvivorRatio=8
>> -XX:MaxTenuringThreshold=5 -XX:CMSInitiatingOccupancyFraction=75
>> -XX:+UseCMSInitiatingOccupancyOnly
>>
>> from yaml
>> in_memory_compaction_limit=64
>> compaction_throughput_mb_sec=8
>> multi_threaded_compaction=false
>>
>>  INFO [AntiEntropyStage:1] 2012-06-29 09:21:26,085 AntiEntropyService.java
>> (line 762) [repair #2b6fcbf0-c1f9-11e1-0000-2ea8811bfbff] MsgIrtConv is
>> fully synced
>>  INFO [AntiEntropySessions:8] 2012-06-29 09:21:26,085
>> AntiEntropyService.java (line 698) [repair
>> #2b6fcbf0-c1f9-11e1-0000-2ea8811bfbff] session completed successfully
>>  INFO [CompactionExecutor:857] 2012-06-29 09:21:31,219 CompactionTask.java
>> (line 221) Compacted to
>> [/home/sas/system/data/ZMail/MsgIrtConv-hc-858-Data.db,].  47,907,012 to
>> 40,554,059 (~84% of original) bytes for 4,564 keys at 6.252080MB/s.  Time:
>> 6,186ms.
>>
>> After this, the logs were fully filled with GC [ParNew/CMS]. ParNew ran
>> for every 3 seconds, while CMS ran for every 30 seconds approx continuous
>> for 40 minutes.
>>
>>  INFO [ScheduledTasks:1] 2012-06-29 09:23:39,921 GCInspector.java (line
>> 122) GC for ParNew: 776 ms for 2 collections, 2901990208 used; max is
>> 8506048512
>>  INFO [ScheduledTasks:1] 2012-06-29 09:23:42,265 GCInspector.java (line
>> 122) GC for ParNew: 2028 ms for 2 collections, 3831282056 used; max is
>> 8506048512
>>
>> .........................................
>>
>>  INFO [ScheduledTasks:1] 2012-06-29 10:07:53,884 GCInspector.java (line
>> 122) GC for ParNew: 817 ms for 2 collections, 2808685768 used; max is
>> 8506048512
>>  INFO [ScheduledTasks:1] 2012-06-29 10:07:55,632 GCInspector.java (line
>> 122) GC for ParNew: 1165 ms for 3 collections, 3264696776 used; max is
>> 8506048512
>>  INFO [ScheduledTasks:1] 2012-06-29 10:07:57,773 GCInspector.java (line
>> 122) GC for ParNew: 1444 ms for 3 collections, 4234372296 used; max is
>> 8506048512
>>  INFO [ScheduledTasks:1] 2012-06-29 10:07:59,387 GCInspector.java (line
>> 122) GC for ParNew: 1153 ms for 2 collections, 4910279080 used; max is
>> 8506048512
>>  INFO [ScheduledTasks:1] 2012-06-29 10:08:00,389 GCInspector.java (line
>> 122) GC for ParNew: 697 ms for 2 collections, 4873857072 used; max is
>> 8506048512
>>  INFO [ScheduledTasks:1] 2012-06-29 10:08:01,443 GCInspector.java (line
>> 122) GC for ParNew: 726 ms for 2 collections, 4941511184 used; max is
>> 8506048512
>>
>> After this, the node got stable and was back and running. Any pointers
>> will be greatly helpful
>>
>>
>
>

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