Newbie question: memcached slow the first time a value is read?
Ask Bjørn Hansen
ask at develooper.com
Wed Dec 7 11:49:52 UTC 2005
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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