R help - Jun 2009 - Determining if swap memory is turned off

In order to run some performance tests on optimization tools, I want to 
be able
to avoid the use of swap memory. In *nix systems, at least Linux ones, I 
can issue
a 'sudo swapoff -a' command and use just the RAM available.  If I
don't
do this, at
some point swap will be used, the disk goes ballistic and the machine is 
unresponsive
because it is thrashing data to the swap.  I suspect others have 
encountered this
too. Clearly I'd rather fail out than get into the thrashing situation. 
Generally I
prefer no swap -- memory is cheap enough that it is easier not to worry 
about these
sorts of woes. However, I'd like to make packages I'm developing 
bullet-proof.

What I need to know is if there are similar facilities on other 
platforms and how to
use them. I see memory.size and memory.limit for Windows -- making R 
less platform
independent -- and they seem to work on a WinXP virtual machine I have 
available.
However, I suspect that the memory.limit includes the swap. When I was 
running
Windoze, I tried valiantly to get the PageFile.sys killed and found it 
kept being set
up again despite following all the recommended steps. (I needed to avoid 
the
plaintext of an encrypted file being "saved" for me!)  I know nothing 
about Mac
swap and how to control it.

Advice welcome.  Below is a crude but self-contained example.

John Nash

## memcrash.R -- try to hit the wall with memory

cat("memcrash.R -- try to hit the wall\n")
cat("You should have swap turned off\n")
temp<-readline("Do you?")
if (temp != "y") stop("Fix swap")

for (j in 1:10) {
   n <- 5^j
   cat("building matrix of order ",n,"\n")
   A<-matrix(nrow=n, ncol=n)
} # end loop

On windows XP | start | Control Panel | System | Advanced |
Performance | Settings | Advanced | Virtual Memory | and select No
Pagefile.  I suspect Vista is similar.

John

2009/6/26 Prof. John C Nash <nashjc at
uottawa.ca>:
> In order to run some performance tests on optimization tools, I want to be
> able
> to avoid the use of swap memory. In *nix systems, at least Linux ones, I
can
> issue
> a 'sudo swapoff -a' command and use just the RAM available. ?If I
don't do
> this, at
> some point swap will be used, the disk goes ballistic and the machine is
> unresponsive
> because it is thrashing data to the swap. ?I suspect others have
encountered
> this
> too. Clearly I'd rather fail out than get into the thrashing situation.
> Generally I
> prefer no swap -- memory is cheap enough that it is easier not to worry
> about these
> sorts of woes. However, I'd like to make packages I'm developing
> bullet-proof.
>
> What I need to know is if there are similar facilities on other platforms
> and how to
> use them. I see memory.size and memory.limit for Windows -- making R less
> platform
> independent -- and they seem to work on a WinXP virtual machine I have
> available.
> However, I suspect that the memory.limit includes the swap. When I was
> running
> Windoze, I tried valiantly to get the PageFile.sys killed and found it kept
> being set
> up again despite following all the recommended steps. (I needed to avoid
the
> plaintext of an encrypted file being "saved" for me!) ?I know
nothing about
> Mac
> swap and how to control it.
>
> Advice welcome. ?Below is a crude but self-contained example.
>
> John Nash
>
> ## memcrash.R -- try to hit the wall with memory
>
> cat("memcrash.R -- try to hit the wall\n")
> cat("You should have swap turned off\n")
> temp<-readline("Do you?")
> if (temp != "y") stop("Fix swap")
>
> for (j in 1:10) {
> ?n <- 5^j
> ?cat("building matrix of order ",n,"\n")
> ?A<-matrix(nrow=n, ncol=n)
> } # end loop
>
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>


-- 
John C Frain
Economics Department
Trinity College Dublin
Dublin 2
Ireland
www.tcd.ie/Economics/staff/frainj/home.html
mailto:frainj at tcd.ie
mailto:frainj at gmail.com