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From David Boyd <>
Subject Re: Optimal configuration for benchmark
Date Thu, 27 Jun 2013 17:11:17 GMT
       I have actually been looking for a more general Giraph benchmark 
and would love to test/play with
what you have.

       To answer your questions we need to first assume a dedicated 
cluster where your test is the only
one running.

        For number of mappers we will assume that your cluster is 
configured in a pseudo-standard one mapper
per core (e.g. the max mappers for each node equals the number of cores 
on that node).     For giraph, due to it
being CPU centric it is pretty important that you not oversubscribe the 

          So for the number of mappers you should use <total cluster 
mappers> - 1.   This is because Giraph needs
one mapper for the master node.

            HEAP_SIZE and are basically 
equivalent (but I prefer the latter).   In any case,
a part of this question depends on the what besides Hadoop is running on 
each node.   Generally, you want each
mapper to have as much heap space as possible.  The goal is to avoid 
swapping, leave enough memory free for buffer
cache, and have enough heap for each task that it does not need to spend 
a ton of time in garbage collection.
I like to look at an idle node and see what the base overhead of used 
memory is.  Then depending on the IO
requirements of my job (especially read IO) reserve a portion of the 
remaining memory for buffer cache and then
divide the remainder by the number of mappers.

               That is sort of the top down approach.  A bottom up 
approach would look at the size of objects being
managed/used in a mapper and compute upwards from there.

                That said a -Xmx 4G would be the low end of what I would 
specify.   Also, you may want to set the options
whcih change how Java does garbage collection.

Hope this helps.

On 6/27/2013 12:20 PM, Christian Krause wrote:
> Hi,
> I implemented a benchmark that allows me to generate an arbitrarily 
> large graph (depending on the number of iterations). Now I would like 
> to configure Giraph so that I can make the best use of my hardware for 
> this benchmark. Based on the number of nodes in my cluster, their 
> amount of main memory and number of cores, I am asking myself how do I 
> determine the optimal parameters of Giraph / Hadoop, specifically:
> - the number of used mappers
> - the HEAP_SIZE environment variable
> - the memory specified in the property
> (any other relevant parameters?)
> Also, I was wondering how well Giraph can handle computations which 
> start with a very small graph and mutate it to a very large one. For 
> example, if I understand correctly the number of mappers is not 
> dynamically adjusted.
> Any hints (or links to documentation) are highly appreciated.
> Cheers,
> Christian

========= ============
David W. Boyd
Director, Engineering
7901 Jones Branch, Suite 700
Mclean, VA 22102
office:   +1-571-279-2122
fax:     +1-703-506-6703
cell:     +1-703-402-7908
============== ============
First Robotic Mentor - FRC, FTC -
President - USSTEM Foundation -

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