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

[Alex Stapleton]

On 7 Dec 2005, at 11:49, Ask Bjørn Hansen wrote:

>
> 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).
>

You may also want to set swappiness to 0 so that Linux is less likely  
to swap it out and will favour eating up the page cache instead.

echo 0 > /proc/sys/vm/swappiness

Should do it. Depends on what else your using the machine for though.