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From Bryan Talbot <bryan.tal...@playnext.com>
Subject Re: OldGen saturation
Date Tue, 28 Oct 2014 17:19:31 GMT
On Tue, Oct 28, 2014 at 9:02 AM, Adria Arcarons <
Adria.Arcarons@greenpowermonitor.com> wrote:

>  Hi,
>
> Hi



>
>
> We have about 50.000 CFs of varying size
>


>
>

>
> The writing test consists of a continuous flow of inserts. The inserts are
> done inside BATCH statements in groups of 1.000 to a single CF at a time to
> make them faster.
>



>
>
> The problem I’m experiencing is that, eventually, when the script has been
> running for almost 40mins, the heap gets saturated. OldGen gets full and
> then there is an intensive GC activity trying to free OldGen objects, but
> it can only free very little space in each pass. Then GC saturates the CPU.
> Here are the graphs obtained with VisualVM that show this behavior:
>
>
>
>
>
> My total heap size is 1GB and the the NewGen region of 256MB. The C* node
> has 4GB RAM. Intel Xeon CPU E5520 @
>


Without looking at your VM graphs, I'm going to go out on a limb here and
say that your host is woefully underpowered to host fifty-thousand column
families and batch writes of one-thousand statements.

A 1 GB java heap size is sometimes acceptable for a unit test or playing
around with but you can't actually expect it to be adequate for a load test
can you?

Every CF consumes some permanent heap space for its metadata. Too many CF
are a bad thing. You probably have ten times more CF than would be
recommended as an upper limit.

-Bryan

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