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From Haoyuan Li <>
Subject Re: off-heap RDDs
Date Mon, 26 Aug 2013 00:06:04 GMT
Hi Imran,

One possible solution is that you can use
When data is in Tachyon, Spark jobs will read it from off-heap memory.
Internally, it uses direct byte buffers to store memory-serialized RDDs as
you mentioned. Also, different Spark jobs can share the same data in
Tachyon's memory. Here is a presentation
we did in May.


On Sun, Aug 25, 2013 at 3:26 PM, Imran Rashid <> wrote:

> Hi,
> I was wondering if anyone has thought about putting cached data in an
> RDD into off-heap memory, eg. w/ direct byte buffers.  For really
> long-lived RDDs that use a lot of memory, this seems like a huge
> improvement, since all the memory is now totally ignored during GC.
> (and reading data from direct byte buffers is potentially faster as
> well, buts thats just a nice bonus).
> The easiest thing to do is to store memory-serialized RDDs in direct
> byte buffers, but I guess we could also store the serialized RDD on
> disk and use a memory mapped file.  Serializing into off-heap buffers
> is a really simple patch, I just changed a few lines (I haven't done
> any real tests w/ it yet, though).  But I dont' really have a ton of
> experience w/ off-heap memory, so I thought I would ask what others
> think of the idea, if it makes sense or if there are any gotchas I
> should be aware of, etc.
> thanks,
> Imran

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