How to reduce memory footprint of a rails app

Rails
1

Hi-

My app has reached the memory limit allotted by my host. Can someone
tell me how I go about reducing the memory footprint? Does rails load
every single gem it finds, and can I somehow throw away the ones I
don’t need? Any other advice or suggestions for strategies or tools
to diagnose where memory is being used would be appreciated.

Thanks,
Dino

2

Are you running many mongrels?

If you are, a solution that is going to use less memory is running on
JRuby with rails thread-safety enabled.

Maurício Linhares
http://alinhavado.wordpress.com/ (pt-br) | http://blog.codevader.com/
(en)

3

dino d. wrote:

My app has reached the memory limit allotted by my host. Can someone
tell me how I go about reducing the memory footprint? Does rails load
every single gem it finds, and can I somehow throw away the ones I
don’t need? Any other advice or suggestions for strategies or tools
to diagnose where memory is being used would be appreciated.

The real question is: what’s hogging up memory? Use theory of
constraints: find the parts of your application that use the most
memory, optimize it, and move on to the next battle.

You should profile and benchmark your application to find out. There’s
lots of tools you could use for that, including railsbench and the
NewRelic/FineRuns/Scout facilities.

Depending on the time you have on your hands it might be cheaper to up
the memory. RAM’s cheap and developer time typically isn’t.

–
Roderick van Domburg
http://www.nedforce.com

4

dino d. wrote:

  1. how do you/can you detect and removed unused gems or modules?

Ideally you’ve never added anything you don’t need and removed things
that became deprecated.

If not: do you have a test suite? Tracking code coverage or just
removing things to see if tests break is a sure-fire way of knowing
what’s required and what’s not.

  1. what kinds of things make memory bloat? can you give me a push in
    the right direction based on experience? do i start in my controllers
    or models, etc.?

In no particular order:

  • Having many routes
  • Using gems that leak (hpricot, feed-normalizer, old versions of
    RMagick)
  • Calling AR#size instead of AR#count where applicable
  • Retrieving large sets of data or columns where you don’t need them
  • Loading binary files into memory

Please do add to the list.

–
Roderick van Domburg
http://www.nedforce.com

5

thanks for the replies. i’m on dreamhost running passenger. their
support is horrible, it takes 48 hours to get an e-mail response.
anyway, i’m just looking to patch up my memory use in the app for the
time being, and i was wondering how i go about decreasing the memory
footprint by either optimizing code or removing unnecessary or unused
gems or plugins. so the two generic questions are :

  1. how do you/can you detect and removed unused gems or modules?
  2. what kinds of things make memory bloat? can you give me a push in
    the right direction based on experience? do i start in my controllers
    or models, etc.?

i have no experience whatsoever in assessing where memory is used in a
rails app and would appreciate any common patterns of opportunity for
mem reduction.

thanks a lot.
dino

On Feb 15, 11:08 am, Roderick van Domburg <rails-mailing-l…@andreas-

6

Hi Dino,

Any chance you are running your development environment instead of
production environment?

If you’re running your dev env, and it’s config’d like a typical
default dev env, each request to the app will re-load the entire
stack, and that stack will be cached. This is so that any changes you
make to the app are immediately reflected in the app on the next
request made on the app, which is what you’d want when your dev’ing
your app. However, the longer you run under dev env, the more memory
that dev env process will consume. This is not the case with a
typical production env setup, in which app code mods would require an
app restart to pick up such mods.

Regardless, if you want to log your app instance(s)'s resource usage
upon each request for analysis purposes (and you’re running under
linux/unix) you could do something like:

in app/controller/application.rb:

…
before_filter :log_resource_usage

…
private

def log_resource_usage
# see ps man page: http://unixhelp.ed.ac.uk/CGI/man-cgi?ps
x,psr,etime,pcpu,pmem,rss,vsz = ps -o psr,etime,pcpu,pmem,rss,vsz -p #{Process.pid}.split(‘\n’)[1].split(/\s+/)
logger.info(“***INFO: resource_usage: rails_env=#{RAILS_ENV} pid=#
{Process.pid} psr=#{psr} etime=#{etime} pcpu=#{pcpu} pmem=#{pmem} rss=#
{rss} vsz=#{vsz} req_method=#{request.method} req_uri=#{request.env
[‘REQUEST_URI’]}”)
end

…

which will produce log entries like:

***INFO: resource_usage: rails_env=development pid=22401 psr=0
etime=14:38:23 pcpu=0.0 pmem=3.1 rss=32620 vsz=59952 req_method=get
req_uri=/testapp/some/such/request

Jeff