I have a Rails 2.3.8 app hosted and running on slicehost (256M). I am not familiar at all with the back-end, I basically followed the steps from the slicehost tutorials to install Apache. The memory usage being very high, I then changed my Apache conf file to reduce the MaxClient number to 10... but my slice is still swapping.
Here is what the memory usage I get after just a few clicks on my site:
top - 23:57:12 up 28 min, 2 users, load average: 0.43, 0.54, 0.30
Tasks: 79 total, 1 running, 78 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.1%us, 0.1%sy, 0.0%ni, 97.8%id, 0.1%wa, 0.0%hi, 0.0%si, 2.0%st
Mem: 262364k total, 258656k used, 3708k free, 260k buffers
Swap: 524280k total, 262772k used, 261508k free, 6328k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4004 web-app 20 0 178m 72m 1888 S 0 28.4 0:04.38 ruby1.8
4001 web-app 20 0 172m 61m 1932 S 0 24.2 0:02.72 ruby1.8
3941 root 20 0 164m 57m 1672 S 0 22.5 0:21.44 ruby
3990 web-app 20 0 209m 21m 1696 S 0 8.4 0:18.00 ruby1.8
3950 web-app 20 0 165m 7464 1548 S 0 2.8 0:20.40 ruby1.8
3684 mysql 20 0 224m 6504 2084 S 0 2.5 0:14.34 mysqld
3938 root 20 0 53632 3048 1036 S 1 1.2 0:01.50 starling
3839 root 20 0 243m 1456 1248 S 0 0.6 0:00.34 apache2
3897 www-data 20 0 243m 1452 1072 S 0 0.6 0:00.04 apache2
3894 www-data 20 0 243m 1368 1008 S 0 0.5 0:00.04 apache2
3895 www-data 20 0 243m 1220 960 S 0 0.5 0:00.02 apache2
3888 root 20 0 46520 1204 1100 S 0 0.5 0:02.29 ruby1.8
3866 root 20 0 17648 1184 896 S 0 0.5 0:00.08 bash
3896 www-data 20 0 243m 1180 952 S 0 0.4 0:00.00 apache2
3964 www-data 20 0 243m 1164 956 S 0 0.4 0:00.02 apache2
3892 www-data 20 0 243m 1132 956 S 0 0.4 0:00.00 apache2
3948 www-data 20 0 243m 1132 956 S 0 0.4 0:00.00 apache2
3962 www-data 20 0 243m 1132 956 S 0 0.4 0:00.02 apache2
3963 www-data 20 0 243m 1132 956 S 0 0.4 0:00.00 apache2
3965 www-data 20 0 243m 1080 888 S 0 0.4 0:00.00 apache2
3887 root 20 0 89008 960 796 S 0 0.4 0:00.00 ApplicationPool
I'm not sure what to do next... I could upgrade to a larger slice but for now I have almost no traffic on this app, so I think it's more a problem with my configuration or maybe my code?
Any concrete recommendations would be welcome! Thanks
It looks like your rails app is using all your available memory. I would recommend three things:
Upgrade the memory on your server. 256MB is not very much for a Rails app. Going to 512 may alleviate your problem. If that solves it, you then need to consider the additional cost ($18/mo) vs how much time it will take to track down performance issues.
Profile your application to figure out which requests are consuming the most memory. This is likely going to be places where you're finding a lot of records and possibly including some associated tables too. There are a couple of tools out there to help you narrow down possible trouble areas. I've used oink but there are definitely others. Once you figure out where the problems are, you can make some tweaks to try and reduce the memory usage.
Assuming you're using Passenger with Apache, you can reduce the number of concurrent requests in the Passenger config file. This might be useful for that https://serverfault.com/questions/15350/running-ruby-on-rails-app-on-apache-passenger-to-much-memory