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From Yiming Sun <yiming....@gmail.com>
Subject Re: key cache size in mb = 0 doesn't work?
Date Tue, 27 Nov 2012 05:23:39 GMT
Thank you very much Andras.  I will try MX4J tomorrow.

Also thanks for the pointers on nodetool.  I just poked around a bit, and
found that "info" would give you the cache statistics, and there are also
"invalidatekeycache" and "invalidaterowcache".  I think these are exactly
what I need.

-- Y.


On Tue, Nov 27, 2012 at 12:14 AM, Andras Szerdahelyi <
andras.szerdahelyi@ignitionone.com> wrote:

>  If its the RMI horror ( registry port + actual port ) you are worried
> about, enabling MX4J in cassandra-env.sh for the HTTP transport (
> http://wiki.apache.org/cassandra/Operations#Monitoring_with_MX4J ) could
> help although i never used it myself. Or you can just throw in the Jolokia
> JVM agent http://www.jolokia.org which will do roughly the same
>
>  i'm not aware of the hit rate or any of the other cf/system metrics
> being exposed over anything other than JMX, sorry. You can poke around with
> nodetool on the nodes themselves ( that uses JMX itself ) to get other
> metrics, but i have not been able to get cache stats out of nodetool
> cfstats. I think it might be because they are no longer on the CF's mbean.
>
>  regards,
> Andras
>
>  On 27 Nov 2012, at 05:22, Yiming Sun <yiming.sun@gmail.com> wrote:
>
> Interesting -- I completely overlooked the OS cache aspect, but how long
> does the OS keep cached pages? It seems they reside in memory for 4 hours
> at least (which happens to be the default time for key cache)..  The CF has
> over 2.6 million rows, and I am only fetching a random set of 5000 each
> time.
>
>  Where else can I examine the cache hit ratio? The nodes are remote
> servers behind some strict university controlled firewall, so it wouldn't
> be easy for me to tap in using JConsole.  Thanks.
>
>  -- Y.
>
>
> On Mon, Nov 26, 2012 at 11:06 PM, Andras Szerdahelyi <
> andras.szerdahelyi@ignitionone.com> wrote:
>
>>
>> SSTables in http://en.wikipedia.org/wiki/Page_cache maybe?
>> How many rows do you have in this CF? Are you getting all columns?
>>
>> What do the cassandra.db mbeans say ( hit ratio, cache requests, items
>> etc )
>>
>> regards,
>> Andras
>>
>> On 27 Nov 2012, at 04:12, Yiming Sun <yiming.sun@gmail.com> wrote:
>>
>> > Hi,
>> >
>> > I am carrying out some performance test against a 6-node cassandra
>> cluster (v1.1.0), and need to disable the key cache entirely as one of the
>> scenarios.
>> >
>> > However, by setting key_cache_size_in_mb to 0, I am still seeing
>> caching effects.  For example, when I fetch a set of 5000 rows, the first
>> time it would deliver at about 60MB/sec, but all subsequent fetches (even
>> after fetching several other sets), it would deliver at about 120MB/sec.
>>  This is exactly the same behavior I have observed when the
>> key_cache_size_in_mb was left blank.
>> >
>> > So I am just wondering how I can disable the key cache entirely.  All
>> our nodes have JNA.jar deployed -- not sure it this has anything to do with
>> what I saw.  Thanks.
>> >
>> > -- Y
>>
>>
>
>

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