curr_items never decreases

Brian Moon brianm at
Thu May 18 13:57:45 UTC 2006

Just Marc wrote:
> Hello,
> I'm using memcached 1.1.12 from Debian unstable, and it seems that even 
> though items do expire (verified by seeing that they are no longer 
> available after the timeout via mc_get), curr_items doesn't decrease, ever.

To make memcached a fast beast, it does lazy clean up (not sure of the 
proper term).  That means, things are not removed just because they 
expire.  They stay in the cache.  If asked for however, and they are 
expired, they are not returned.  This makes for a much simpler, and 
faster cache system.

IMO, the key metrics to watch when deciding if the cache is effective is 
the hits and misses.  We have a hit/miss ratio of about 900:1.  After a 
while, you learn not to worry about the number of items, size, etc.  As 
long as you have a good hit/miss ratio things are working well for you.

And, before you wonder, no, there is no current way to get a count of 
unexpired items from the cache.


Brian Moon
Its good to be cheap =)

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