Newbie question: memcached slow the first time a value is read?

[Ask Bjørn Hansen]

On Dec 7, 2005, at 3:27 AM, Tim Strehle wrote:

> - So I installed memcached (memcached-1.1.12 with libevent-1.1a on  
> SuSE Linux 9.3, kernel version 2.6.11.4-21.9-bigsmp, single Xeon  
> 2.4 GHz with 3 GB RAM) and the PHP PECL memcache extension  
> (memcache-1.5 on PHP 4.4.0), started memcached with 1.5 GB RAM  
> ("memcached -d -u digicol -m 1536 -M -l 127.0.0.1 -p 11211") and  
> ran a PHP script to fill it with the metatdata for those 2.5  
> million documents.
>
> I understand from "top" that my PHP script wrote 1145 MB of data  
> into memcached:
>
> ====================================================================== 
> ==
> Tasks:  73 total,   1 running,  72 sleeping,   0 stopped,   0 zombie
> Cpu(s):  0.0% us,  0.2% sy,  0.0% ni, 99.3% id,  0.5% wa,  0.0%  
> hi,  0.0% si
> Mem:   3111540k total,  1868280k used,  1243260k free,   833312k  
> buffers
> Swap:  2104472k total,   479964k used,  1624508k free,    86204k  
> cached
>
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> 13278 digicol   16   0 1145m 739m  468 S  0.0 24.4   2:38.86 memcached

If I'm reading this right (darn proportional fonts) then yes, you are  
swapping memcached!

(and/or you are swapping something else which on most webservers is a  
terribly terribly thing to do).


  - ask

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