Track memory usage in Fortran 90

Question

I am trying to track the memory usage and cpu time of a subroutine in a Fortran 90 program. To track the track the cpu time, I use the following:

call cpu_time(tic) call subroutine(args) call cpu_time(toc) time = toc-tic

Is there a way to do something similar to record memory usage? What is the best way to do this? Thanks in advance for the help.

Answer 1

liskawc has a very nice solution and I've been looking for something like this for a while.

He asked for feedback, and there were a couple of areas that could be improved.

• there are several system calls that can be eliminated by just reading the system file directly from your Fortran program
• the solution depends on a temporary file in the users directory
• my fortran compiler didn't like opening a file starting with the tilde

I've modified his original program to overcome these issues:

subroutine system_mem_usage(valueRSS)
implicit none
use ifport !if on intel compiler
integer, intent(out) :: valueRSS

character(len=200):: filename=' '
character(len=80) :: line
character(len=8)  :: pid_char=' '
integer :: pid
logical :: ifxst

valueRSS=-1    ! return negative number if not found

!--- get process ID

pid=getpid()
write(pid_char,'(I8)') pid
filename='/proc/'//trim(adjustl(pid_char))//'/status'

!--- read system file

inquire (file=filename,exist=ifxst)
if (.not.ifxst) then
  write (*,*) 'system file does not exist'
  return
endif

open(unit=100, file=filename, action='read')
do
  read (100,'(a)',end=120) line
  if (line(1:6).eq.'VmRSS:') then
     read (line(7:),*) valueRSS
     exit
  endif
enddo
120 continue
close(100)

return
end subroutine system_mem_usage

Please feel free to update if you can improve this program any further!

Answer 2

By memory usage i will assume you want RSS at a given moment in your program on a linux machine. If you dont want to use a profiler, then this routine might help a bit:

I use this routine (which actually quite ugly to be honest) but worked so far. Brief description of subroutine:

when you call the subroutine it issues a series of system calls, that search within the /proc/ filesystem information about your program. whatever is in there you can get, if you modify this sub, i use this one specifically to get RSS value for example. The routine returns valueRSS as a character, which you can then write to a specific file if you wish to have a profile of how ram usage is within your program. You could also convert the string to a number, but i leave that to you if you need it.

subroutine system_mem_usage(valueRSS)
 use ifport !if on intel compiler
 character(len=30) :: count_char,pid_char, dummy
 character(len=200) :: filename
 character(len=200) :: command
 integer :: count,pid,res
 character(len=50), intent(out) :: valueRSS

 call system_clock(count)

 pid=getpid()

 write(count_char,'(I10)') count
 write(pid_char,'(I10)') pid

 filename='~/tmp/mem_use.'//trim(count_char)

 command='cat /proc/'//trim(adjustl(pid_char))//'/status >'//trim(adjustl(filename))

 res=system(command)

 command='cat '//trim(adjustl(filename))//' | grep RSS > ~/tmp/rss_use.'//trim(count_char)

 res=system(command)

 open(unit=100, file='~/tmp/rss_use.'//trim(count_char))
 read(100,*) dummy, valueRSS
 close(100)

 return
end subroutine

if you are interested in some other value than RSS, then just edit the part at "grep RSS". This subroutine also assumes you have a tmp directory within your home.

Oh yea, feel free to modify the script as you wish and if anyone has any ideas on how to do this more elegantly i would much appreciate it.