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From Kyusik Chung <kyu...@discovereads.com>
Subject Re: Memory usage continually increases with reads
Date Wed, 28 Apr 2010 23:28:20 GMT
Isnt setting swappiness to a lower value a good idea only if you know you have the physical
RAM to support it?  What Im observing on my box is that jsvc uses up all the physical RAM.
 Its VM size is 4-5GB right now (not sure if it will continue to grow).

Apologies if Im misunderstanding how the swappiness factor works...its new to me.

Kyusik Chung

On Apr 28, 2010, at 3:28 PM, Time Less wrote:

> This sounds similar to /proc/sys/vm/swappiness misconfiguration. Is it zero or close
to zero? If setting it 0 solves your problem, make sure all your nodes get this:
> 
> /etc/sysctl.conf:
>   vm.swappiness=0
> 
> 
> On Wed, Apr 28, 2010 at 12:12 PM, Kyusik Chung <kyusik@discovereads.com> wrote:
> Hello.  I am using Cassandra 0.6.1 on ubuntu 8.04.  3 node cluster.
> 
> I notice that when I start making lots of read requests (serially), memory usage of jsvc
keeps climbing until it uses up all memory on the server (happens for all 3 servers in the
cluster).  At that point, the box starts swapping a little (but not too much) and performance
is degraded.  Read performance does not drop off a cliff, but it does take a serious hit (maybe
50%).
> 
> I have tried setting Xmx to various different values, but it doesnt seem to limit the
growth in memory usage.  I understand that I should expect to see jsvc use a bit more memory
than what the jvm is configured to use, but it doesnt seem to be limited to just an overhead.
 I have set Xmx all the way down to 128M (just to test) and still jsvc will use up 2G of memory.
> 
> Are there other settings that I should be changing?
> 
> Note that when I test by simply running a lot of writes but no reads, jsvc seems to respect
the Xmx value.
> 
> Thanks!
> 
> Kyusik Chung
> 
> -- 
> timeless(ness)


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