"SERVER_ERROR out of memory" when changing cache entry pattern

Dustin Sallings dustin at spy.net
Wed Aug 29 17:14:13 UTC 2007

On Aug 29, 2007, at 2:44 , Alexander Zaitsev wrote:

> Here is how it happened. Cache was full with more or less uniform
> objects: long key and boolean value. I have switched the pattern of
> cache entries that my application generates to have shorter key but  
> few
> hundred bytes value. This resulted in immediate "out of memory" on
> storing any new value in the cache. Looks like memcached could not
> allocate space for the bigger object than cache contained before. I.e.
> it tried to release LRU entries, but it was not enough to get the
> required space, because old entries were significantly smaller than  
> new
> ones.

	This is more likely due to suboptimal slab classes.  If you start  
memcached with -vv you'll see the slab definitions.  You'll want a  
pretty small chunk growth factor for uniform entries like that.

	BTW, I'd strongly recommend not running memcached (or any other  
process when you can avoid it) as root.

Dustin Sallings

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