ls/ls -lrt Limitation [Insufficient or invalid memory ]

Hi, Some times we may face this problem about ls or ls -lrt if we have millions of files.

Its because system virtual memory settings or having less in size.

His problem is that ls can't sort the large directory because of too low a memory ulimit. He should either change the relevant kernel tunables for the memory limits (both hard and soft, for
both data and total virtual memory), or simply up the ulimit -v and ulimit -d settings from the (Bourne or Korn) shell. Only root can do either, of course.

In many cases the solution is the ls -f option, which suppresses the sorting and gives the directory contents in a sort-of random way, similar to find (or DOS, for that matter!)