Re: Estimating the right cache size...

[Tobias Downer <toby@xxxxxxxxx>]

Martin Cordova S. wrote:

> Hi, I have a McKoi server installation for production with 512MB RAM, Linux
> SuSE 8,1 with only the essential services:
> 
> network
> cron
> kbd
> sshd
> 
> and of course mckoidb
> 
> I assigned -Xms256 -Xmx256 to McKoi process, but only the default 4MB of
> cache. The other 256MB are reserved for Linux.

I would remove the '-Xms256' argument and let the JVM decide how much 
memory it needs.

> Questions:
> 
> 1) May I take from Linux more RAM, considering that Linux is loading very
> few services? or I that may degrade vital OS functions?

It's difficult to tell you exactly what needs to be done to optimize a 
server.  In Linux, more free RAM means more cache space for the file 
system so it's a good idea not to utilize all RAM with the services 
running on your server.


> 2) Will McKoi benefit from a larger cache? How big could it be? considering
> the actual 256MB dedicated to McKoi

Absolutely, we have our Mckoi configuration set at 12MB cache for the 
Mckoi mailing list archives.  If your statistics are telling you that 
Mckoi is cleaning the cache a lot, then you will benefit from a larger 
cache size.  Theoretically you can set the cache size at whatever size 
you like, however at some threshold there will be no benefit to having 
such a large cache.  Unfortunately there's no easy way to determine what 
that threshold is and experimentation is necessary.

Toby.