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From Girish Kumar <girishkuma...@gmail.com>
Subject Re: Large # of Pending Tasks?
Date Mon, 26 Aug 2013 16:49:14 GMT
I'm running "ReleaseVersion: 1.2.5-SNAPSHOT" version.

-------------------------------------------------------------------------------------------------

Well, I see that REQUEST_RESPONSE is capped at # processor count (below
code).  The foreground writers and readers are still set at what c*.yaml
says.

May be the pending task pile up is because the response handlers are unable
to catch up with foreground writer/reader tasks ?  comments?

Thanks,
/BK




 stages.put(Stage.MUTATION, multiThreadedConfigurableStage(Stage.MUTATION,
getConcurrentWriters()));
        stages.put(Stage.READ, multiThreadedConfigurableStage(Stage.READ,
getConcurrentReaders()));
        stages.put(Stage.REQUEST_RESPONSE,
multiThreadedStage(Stage.REQUEST_RESPONSE,
FBUtilities.getAvailableProcessors()));
        stages.put(Stage.INTERNAL_RESPONSE,
multiThreadedStage(Stage.INTERNAL_RESPONSE,
FBUtilities.getAvailableProcessors()));


On Mon, Aug 26, 2013 at 8:36 PM, Nate McCall <nate@thelastpickle.com> wrote:

> Interesting - my understanding is that the only places where stages are
> capped at "available processors" have to do with clustering operations (see
> the static initializer in o.a.c.concurrent.StageManager).
>
> What version are you using, by the way? Most likely I'm missing something
> though.
>
>
> On Mon, Aug 26, 2013 at 9:36 AM, Girish Kumar <girishkumarbk@gmail.com>wrote:
>
>> This is the 'Active Count' as observed on jconsole under
>> 'org.apache.cassandra.request' ReadStage->Attributes.  Below details...
>>
>>
>> ActiveCount -> 12
>> ..
>> Core Pool Size -> 192
>> Core Threads -> 192
>> CurrentlyBlockedTasks ->  0
>> MaximumThreads -> 192
>> PendingTasks -> 691
>> TotalBlockedTasks -> 0
>>
>> I expect active count to go upto 192 as those many threads are available
>> to handle requests ? Am I missing reading something here?
>>
>> I observe that Active Count never goes beyond 24 and Pending Tasks Count
>> keeps building up?
>>
>> So question is what's the relation between Active count and max threads
>> available in the pool for execution?
>>
>> Thanks,
>> /BK
>>
>>
>>
>>
>>
>> On Mon, Aug 26, 2013 at 7:28 PM, Nate McCall <nate@thelastpickle.com>wrote:
>>
>>> I'm not quite sure what you mean by 'active task count' - what is the
>>> output of 'nodetool tpstats' when you run this test?
>>>
>>>
>>> On Mon, Aug 26, 2013 at 4:39 AM, Girish Kumar <girishkumarbk@gmail.com>wrote:
>>>
>>>> Hi,
>>>>
>>>> I'm using a single node Cassandra on 24 Core/48GB system.  I have set
>>>> my writers and readers (in yaml) to be around 192 for both and read and
>>>> write.  In this mode, when stressed with 192 threads for inserts and reads,
>>>> what I observed via the jconsole of 'client request' the active read and
>>>> write tasks never go beyond 24.  However there are as many as 192 pending
>>>> tasks.  I was expecting Cassandra server to utilize the threads that
>>>> are created using yaml and perform as many parallel inserts and reads.
>>>>
>>>> Why cassandra active task count doesn't go beyond 24 when the actual
>>>> writers and readers are around 192 ?
>>>>
>>>> Any thoughts?
>>>> /BK
>>>>
>>>
>>>
>>
>

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