question about the LRU

dormando dormando at
Thu Jan 3 18:43:14 UTC 2008

Please try with a memcached instance set to 64 megabytes or higher. It 
won't properly allocate all of the slab instances if memory values are 
much lower than the defaults. Causes all sorts of weirdness.

Try ramping up the RAM, try what brian moon said, and if you still see 
this behavior please submit a script to the ML to repeat it, for 


Mathieu Viel wrote:
> Hi guys. I have a question about the cache structure.
> I want to use memcached to store some frequently used data chuncks and 
> the idea is to always have in memcached the most frequent requested 
> data;  if  i insert some new data when the memory for memcached is fully 
> used, i want the least requested data to be replaced.
> I noticed in the FAQ that the cache structure is an LRU so i thought 
> "great i'll have almost nothing to do to implement this!" but, in order 
> to make sure, i ran some tests and i am dissapointed about the results.
> With a 1Mb memcached, i first set an item with "1_1_1" as key and "1" as 
> value; i then get the value of this item (which is working ^^) and then 
> set some new randoms items i will never retrieve in order to fill the 
> memory (i made sure the key value will never be "1_1_1" for these 
> items); i then get the value of my "1_1_1" item to check if it's still 
> there. This "simple" process is working fine but when the memory is 
> filled, after some time, i can't get the value of my "1_1_1" item 
> anymore :S
> I tried to check in verbose mode (-vv) and i can't get any interesting 
> information about this "issue".
> I thought that since i frequently get the value of this item, it would 
> not make it the LRU one so its would never be somehow erased. Am i 
> wrong? I know about the different slabs sizes but since i always set the 
> value to "1", i think all these items are in the same category.
> Thanks for help!
> -- 
> Vivi

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