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From Henry Robinson <he...@cloudera.com>
Subject Re: impala process create too many thread (in our cluster 200 service sometimes over 15000+)
Date Mon, 28 Mar 2016 23:36:10 GMT
Zhen -

You're right, Impala does create a lot of threads, and the vast majority
are in the RPC handlers. I'm going to work on reducing this number in the
next couple of months - it's a little trickier than changing the Thrift
server mode, unfortunately.

However, these threads are long-lived, so there's not much overhead from
thread creation or destruction. The main cost is the extra memory for the
stacks, and context-switching overhead. Neither show up on our profiles,
but on larger clusters we do hit ulimits occasionally.

Watch this space :)

Henry

On 26 March 2016 at 14:13, Silvius Rus <srus@cloudera.com> wrote:

> +dev@impala.incubator.apache.org, Henry, Marcel
> bcc:impala-dev@cloudera.org
>
> I believe this is documented as
> https://issues.cloudera.org/browse/IMPALA-1514.
>
> Henry, Marcel, do you know if this will be worked on as part of upcoming
> scalability improvements?
>
> On Fri, Mar 25, 2016 at 8:54 PM, zhen <yyzzjj0515@gmail.com> wrote:
>
>>
>> Recently debug impala performance found that the number of threads
>> suddenly high and low
>>
>>
>> About two cases
>>
>> 1. A complex query  will have many fragments
>> 2. big cluster    example :200  impala ins
>> 3. many query running
>>
>> just now  impala do not have thread pool
>> a .ThriftServer use thread mode
>> b. stream sender async channel
>> will  create large volumes of  threads ,as everyone knows thread create
>>  destroy is   high cost  in performance!!
>>
>> what is the next plan TODO
>>
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>
>


-- 
Henry Robinson
Software Engineer
Cloudera
415-994-6679

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