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I've got running a VPS at Linode with 1024 MB RAM, Ubuntu 11.04 and Nginx+PHP-FPM+APC Varnish+Memcached active. I've setup a couple of test blogs with WordPress 3.2.1 and everything works, and the performance tests seem promising: 

# ab -n 1000 -c 100 http://mydomain.com/ This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking mydomain.com (be patient) Completed 100 requests Completed 200 requests Completed 300 requests Completed 400 requests Completed 500 requests Completed 600 requests Completed 700 requests Completed 800 requests Completed 900 requests Completed 1000 requests Finished 1000 requests Server Software: nginx Server Hostname: mydomain.com Server Port: 80 Document Path: / Document Length: 5677 bytes Concurrency Level: 100 Time taken for tests: 0.186 seconds Complete requests: 1000 Failed requests: 0 Write errors: 0 Total transferred: 5989000 bytes HTML transferred: 5677000 bytes Requests per second: 5376.14 [#/sec] (mean) Time per request: 18.601 [ms] (mean) Time per request: 0.186 [ms] (mean, across all concurrent requests) Transfer rate: 31443.08 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 6 9 0.9 8 13 Processing: 4 9 1.3 9 14 Waiting: 1 5 2.5 5 13 Total: 12 18 1.6 18 22 WARNING: The median and mean for the initial connection time are not within a normal deviation These results are probably not that reliable. Percentage of the requests served within a certain time (ms) 50% 18 66% 19 75% 19 80% 19 90% 20 95% 21 98% 22 99% 22 100% 22 (longest request)

After installing Memcached and php5-memcache packages and enabling the WP Memcache plugin I can see the memcache server is up and running, with around a 50% of hits.The memcache service is using 64 MB of memory: 

# ps xa |grep memcached 12259 ? Sl 0:01 /usr/bin/memcached -m 64 -p 11211 -u memcache -l 127.0.0.1

What I can see, though, is a high consumption of main memory and swap, and I'd like to know if this is normal. The server is idle most of the time (the test blogs are running, but no one nows about them so I'm the only visitor), so I can't understand why the memory and swap are so high.

#free -m total used free shared buffers cached Mem: 927 906 21 0 6 58 -/+ buffers/cache: 840 87 Swap: 255 255 0

Any ideas?

Update: Seems Memcached is not the reason. I've stopped the server, the site is of course running, but the mem/swap consumption is still almost 100%. So there should be a problem, maybe with PHP-FPM or Varnish?

Update2: Seems PHP-FPM is the problem, look at this (thanks for the command, Tomtezky)

# ps aux --sort=-rss | head -15 USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND www-data 12414 0.0 9.6 247840 91772 ? S 01:25 0:06 php-fpm: pool www www-data 12405 0.0 9.5 244012 91212 ? S 01:25 0:06 php-fpm: pool www www-data 12418 0.0 9.0 241820 86132 ? S 01:25 0:05 php-fpm: pool www www-data 12417 0.0 8.5 236724 81500 ? S 01:25 0:07 php-fpm: pool www www-data 12409 0.0 8.2 241980 78784 ? S 01:25 0:05 php-fpm: pool www www-data 12407 0.0 8.1 236968 77880 ? S 01:25 0:05 php-fpm: pool www www-data 12400 0.0 8.1 234344 77860 ? S 01:25 0:06 php-fpm: pool www www-data 12408 0.0 8.1 237120 77700 ? S 01:25 0:06 php-fpm: pool www www-data 12410 0.0 8.0 232248 76224 ? S 01:25 0:06 php-fpm: pool www www-data 12413 0.0 7.6 242092 72452 ? S 01:25 0:07 php-fpm: pool www www-data 12416 0.0 7.1 241812 68148 ? S 01:25 0:05 php-fpm: pool www www-data 12412 0.0 7.0 220684 66644 ? S 01:25 0:04 php-fpm: pool www www-data 12402 0.0 6.9 241556 66156 ? S 01:25 0:05 php-fpm: pool www www-data 12419 0.0 6.2 238016 59304 ? S 01:25 0:04 php-fpm: pool www

Seeing that... how to reduce PHP-FPM's memory use?

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  • What is the output of ps aux --sort=-rss | head -15? Commented Aug 19, 2011 at 12:11
  • Output added TOmetzky, seems PHP-FPM is the responsible for that memory consumption, isn't it? Commented Aug 19, 2011 at 18:52
  • Would you mind posting your configs for nginx, php-fpm and memcached? Thanks. Commented Dec 26, 2011 at 17:52
  • JennyMac, doesn't matter, the problem was solved when I found where was the right path for the php5-fpm config files. Thanks! Commented Dec 29, 2011 at 16:04
  • javipas, I was actually trying to setup something similar to what you have, but I cannot get results similar or close to yours. Would you mind sharing your configs with me? I would appreciate it very much, hope you don't mind. Thank you. Commented Dec 30, 2011 at 1:51

1 Answer 1

Reset to default
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It isn't PHP-FPM, it's the Wordpress instance loaded in PHP-FPM. Limit the number of php-fpm workers, or trim down the memory footprint of your wordpress install.

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  • I guessed changing the number of workers could work, but there is an additional problem, described in the AskUbuntu forum /askubuntu.com/questions/57875/…(. THe php5-fpm package does not install properly on Ubuntu 11.04, and it doesn't load the proper config file. So where do I have to create the php-fpm.conf file to restart php5-fpm with the right parameters? Commented Aug 19, 2011 at 23:33
  • I've finally found the config file. It's /etc/php5/fpm/pool.d/www.conf. There I can set up pm.start_servers and the rest of the parameters that allow me to reduce memory usage by PHP-FPM, but your suggestion is correct, thanks. Commented Aug 19, 2011 at 23:48

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