R Cannot allocate memory though memory seems to be available - r

Question

After running several models I need to run a system() command on my R script to shutdown my EC2 instance, but when I get to that point I get:
cannot popen 'ls', probable reason 'Cannot allocate memory'
Note: for this question I even tried ls which did not work
The flow of my script is the following
Load Model (about 2GB)
Mine documents and write to a MySQL database
The above steps are repeated around 20 times with different models with an average size of 2GB each
Terminate the instance
At this point is when I need to call system("sudo shutdown -h now") and nothing happens, but when I try system("sudo shutdown -h now",intern=TRUE) I get the allocation error.
I tried rm() for all my objects just before calling the shutdown, but the same error persists.
Here is some data on my system which is a large EC2 Ubuntu instance
R version 2.15.1 (2012-06-22)
Platform: x86_64-pc-linux-gnu (64-bit)
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=C LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] splines stats graphics grDevices utils datasets methods
[8] base
other attached packages:
[1] RTextTools_1.3.9 tau_0.0-15 glmnet_1.8 Matrix_1.0-6
[5] lattice_0.20-10 maxent_1.3.2 Rcpp_0.9.13 caTools_1.13
[9] bitops_1.0-4.1 ipred_0.8-13 prodlim_1.3.2 KernSmooth_2.23-8
[13] survival_2.36-14 mlbench_2.1-1 MASS_7.3-21 rpart_3.1-54
[17] e1071_1.6-1 class_7.3-4 tm_0.5-7.3 nnet_7.3-4
[21] tree_1.0-31 randomForest_4.6-6 SparseM_0.96 RMySQL_0.9-3
[25] ggplot2_0.9.1 DBI_0.2-5
loaded via a namespace (and not attached):
[1] colorspace_1.1-2 dichromat_1.2-4 digest_0.5.2 grid_2.15.1
[5] labeling_0.2 memoise_0.1 munsell_0.3 plyr_1.7.1
[9] proto_0.3-9.2 RColorBrewer_1.0-5 reshape2_1.2.1 scales_0.2.1
[13] slam_0.1-25 stringr_0.6.1
gc() returns
used (Mb) gc trigger (Mb) max used (Mb)
Ncells 1143171 61.1 5234604 279.6 5268036 281.4
Vcells 1055057 8.1 465891772 3554.5 767962930 5859.1
I noticed that if I run just 1 model instead of the 20 it works fine, so it might be that memory is not getting free after each run although I did rm() the used objects
I also noticed that if I close R and restart it and then call system() it works. If there is a way to restart R within R then maybe I can add that to my script.sh flow.
Which would be the appropriate way of cleaning all of my objects and letting the memory free for each loop so when I need to call the system() commands there is no memory issue?
Any tip in the right direction will be much appreciated!
Thanks

Answer 1

I'm just posting this because it's too long to fit in the comments. Since you haven't included any code, it's pretty hard to give advice. But, here is some code that maybe you can think about.
wd <- getwd()
assign('.First', function(x) {
require('plyr') #and whatever other packages you're using
file.remove(".RData") #already been loaded
rm(".Last", pos=.GlobalEnv) #otherwise won't be able to quit R without it restarting
setwd(wd)
}, pos=.GlobalEnv)
assign(".Last", function() {
system("R --no-site-file --no-init-file --quiet")
}, pos=.GlobalEnv)
save.image() #or only save the things you want to be reloaded.
q("no")
The idea is that you save the things you need in a file called .RData. You create a .Last function that will be run when you quit R. The .Last function will start a new session of R. And you create a .First function that will be run as soon as R is restarted. The .First function will load packages you need and clean up.
Now, you can quit R and it will restart loading the things you need.
(q("no") means don't save, but you already saved everything you need in .RData which will be loaded when it restarts)