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From Leif Hedstrom <>
Subject Re: why does cache hit rate tail off?
Date Wed, 14 Jul 2010 16:11:52 GMT
On 07/14/2010 10:02 AM, Rob Maidment wrote:
> The old (LRU) algorithm made little difference.
> I guess it could be that I’m simply exceeding the cache capacity.  The 
> test uses a working set of 2.24GB.  How do I configure the size of the 
> cache?

Two settings:

In etc/trafficserver/storage.config, you will see a line similar to

     var/trafficserver 140M

You'll want that closer to  2.24G I imagine :). For the RAM cache, the 
setting is in etc/trafficserver/records.config:

     CONFIG proxy.config.cache.ram_cache.size INT -1

The default (-1) means it'll calculate the RAM cache size based on the 
disk cache size; For every 1GB of disk cache, it uses 1MB of RAM cache 
(which is really small honestly). I'd definitely bump this up as much as 
your box can handle, but make sure to leave room for the connections and 
other buffers (setting this is a "trial and error", and is very 
application specific). Fwiw, an inactive connection consumes about 32KB 
of memory, and an active one doubles that (for additional buffers). SSL 
connections consumes even more memory. (I think this is an area where we 
might be able to improve too, patches are welcomed).

I hope any of this helps your benchmarks (really looking forward to see 
your results).

-- leif

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