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From Chris Lohfink <clohfin...@gmail.com>
Subject Re: what is MemtableReclaimMemory mean ??
Date Tue, 02 May 2017 02:36:46 GMT
Question though, how many tables do you have? If you have more than a few
hundreds it could be bottlenecking the flushing if it is flushing very
frequently.

On Mon, May 1, 2017 at 9:32 PM, Chris Lohfink <clohfink85@gmail.com> wrote:

> Theres a read barrier to stop reclaiming a memtable when there are
> requests actively reading it. The *MemtableReclaimMemory* pool offloads
> that wait instead of blocking the caller. It in itself is not going to use
> any cpu or increase load. It will however block the releasing of the
> memtable resources which might cause additional heap allocation pressure.
> Its more likely a symptom of GCs or reads being slow than the cause of the
> issue however.
>
> Chris
>
> On Mon, May 1, 2017 at 9:01 PM, Pranay akula <pranay.akula2323@gmail.com>
> wrote:
>
>> Hi Alain,
>>
>> when  "*MemtableReclaimMemory*"  Pending Tasks increasing, its slowly
>> backing up reads and writes mostly writes. yes i am seeing bit high GC
>> pressure, currently we are using 24Gb Heap  and G1GC collection. I tried
>> changing Memtable flush threshold it did helped a little but not much. I am
>> not seeing any Errors in the Logs.
>>
>>
>> Thanks
>> Pranay.
>>
>> On Thu, Apr 27, 2017 at 6:08 AM, Alain RODRIGUEZ <arodrime@gmail.com>
>> wrote:
>>
>>> Hi Pranay,
>>>
>>> According to http://docs.datastax.com/en/ca
>>> ssandra/3.0/cassandra/tools/toolsTPstats.html, "*MemtableReclaimMemory*"
>>> is the thread pool used for "Making unused memory available". I don't know
>>> much about it since it was never an issue for me. Neither did I heard much
>>> about it.
>>>
>>>
>>>    - Are pending tasks staying high for a long period? `watch -d
>>>    nodetool tpstats`
>>>    - What are your GC settings?
>>>    - Any other threads pending, blocked or dropped?
>>>    - Do you have errors or warnings in your logs?
>>>    - Any GC pressure? (monitored through charts or logs at INFO level,
>>>    or WARN on recent versions)
>>>
>>>
>>> C*heers,
>>> -----------------------
>>> Alain Rodriguez - @arodream - alain@thelastpickle.com
>>> France
>>>
>>> The Last Pickle - Apache Cassandra Consulting
>>> http://www.thelastpickle.com
>>>
>>>
>>>
>>> 2017-04-16 16:04 GMT+02:00 Pranay akula <pranay.akula2323@gmail.com>:
>>>
>>>> Hi,
>>>>
>>>> what is *MemtableReclaimMemory* mean in nodetooltpstats ?? does this
>>>> mean trying to flushing memtable from memory to SStables.
>>>>
>>>> I can see sometimes increase in pending tasks of  MemtableReclaimMemory
>>>> in nodetool tpstats, at that time i can see increase in load on those nodes.
>>>>
>>>> Does decreasing memtable_cleanup_threshold will help ??
>>>>
>>>> Thanks
>>>> Pranay.
>>>>
>>>
>>>
>>
>

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