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Posted to user@spark.apache.org by Johan Verwey <jo...@gmail.com> on 2014/02/17 20:50:06 UTC

Fwd: Why is Spark not using all cores on a single machine?

When I run some of the Apache Spark examples in the Spark-Shell or as a
job, I am not able to achieve full core utilization on a single machine.
For example:

var textColumn = sc.textFile("/home/someuser/verylargefile.txt").cache()

var distinctWordCount = textColumn.flatMap(line => line.split('\0'))

                             .map(word => (word, 1))

                             .reduceByKey(_+_)

                             .count()

When running this script, I mostly see only 1 or 2 active cores on my 8
core machine. Isn't Spark supposed to parallelize this?

This job takes about 15 seconds but most of my cores are idle...

How can I configure spark to utilize all cores?

RE: Fwd: Why is Spark not using all cores on a single machine?

Posted by "Ganelin, Ilya" <Il...@capitalone.com>.
To set the number of spark cores used you must set two parameters in the actual spark-submit script. You must set num-executors (the number of nodes to have) and executor-cores (the number of cores per machinel) . Please see the Spark configuration and tuning pages for more details.


-----Original Message-----
From: ll [duy.huynh.uiv@gmail.com<ma...@gmail.com>]
Sent: Saturday, November 08, 2014 12:05 AM Eastern Standard Time
To: user@spark.incubator.apache.org
Subject: Re: Fwd: Why is Spark not using all cores on a single machine?


hi.  i did use local[8] as below, but it still ran on only 1 core.

val sc = new SparkContext(new
SparkConf().setMaster("local[8]").setAppName("abc"))

any advice is much appreciated.



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Re: Fwd: Why is Spark not using all cores on a single machine?

Posted by ll <du...@gmail.com>.
hi.  i did use local[8] as below, but it still ran on only 1 core.

val sc = new SparkContext(new
SparkConf().setMaster("local[8]").setAppName("abc"))

any advice is much appreciated.



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Re: Fwd: Why is Spark not using all cores on a single machine?

Posted by Johan Verwey <jo...@gmail.com>.
Thank you!!!


On 17 February 2014 12:09, Ewen Cheslack-Postava <me...@ewencp.org> wrote:

> You need to tell it to use more cores by specifying MASTER=local[N] where
> N is the number of cores you want to use. See the "Initializing Spark" and
> "Master URLs" sections of the scala programming guide:
> http://spark.incubator.apache.org/docs/latest/scala-programming-guide.html
>
> Ewen
>
>  Johan Verwey <jo...@gmail.com>
>  February 17, 2014 at 11:50 AM
>
>

Re: Fwd: Why is Spark not using all cores on a single machine?

Posted by Ewen Cheslack-Postava <me...@ewencp.org>.
You need to tell it to use more cores by specifying MASTER=local[N] 
where N is the number of cores you want to use. See the "Initializing 
Spark" and "Master URLs" sections of the scala programming guide: 
http://spark.incubator.apache.org/docs/latest/scala-programming-guide.html

Ewen
> Johan Verwey <ma...@gmail.com>
> February 17, 2014 at 11:50 AM
>