The ksh -x command using high memory.

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 8
  • ksh-20120801-257.el8.x86_64

Issue

  • The ksh -x command using high memory.
Tasks: 140 total,   3 running, 137 sleeping,   0 stopped,   0 zombie
%Cpu(s): 11.9 us, 29.5 sy,  0.0 ni, 55.3 id,  1.1 wa,  0.8 hi,  1.0 si,  0.3 st
MiB Mem :   1274.3 total,     19.1 free,   1224.7 used,     30.6 buff/cache
MiB Swap:   1232.0 total,    823.1 free,    408.9 used.     22.3 avail Mem 

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND                           
   4453 root      20   0 1424972   1.0g    380 D  53.8  78.6   0:01.64 ksh                          
     60 root      20   0       0      0      0 R  23.6   0.0   0:00.72 kswapd0                           
     32 root      20   0       0      0      0 S   1.6   0.0   0:00.05 kcompactd0                        
   3178 root      20   0   19072     56     56 S   0.7   0.0   0:00.10 bash

Resolution

  • The issue is been fixed through Errata under private BZ-2226653 through ksh-20120801-259.el8.

Diagnostic Steps

  • Follow the below steps to check for the issue.

    Note: Running the below test script will lead to high memory usage and out of memory situation.

  1. Run the ksh -x with any script which will read the line. Example as below:

    a. Testing script:

   # cat make_test_data.sh
        N=685133
        while (( N > 0 ))
        do
            date >> test.data
            (( N = N - 1 ))
        done

   # sh make_test_data.sh
   # cat tt.sh
        VAR=`cat test.data`
        echo "sizeof(VAR) = ${#VAR}"

b. The make_test_data.sh will create a file test.data. The generated file is scanned through tt.sh which is been executed with ksh shell.

c. Run ksh -x tt.sh.

  1. Run the top command simultaneously on the other terminal to see the usage for the ksh.
Tasks: 101 total,   3 running,  98 sleeping,   0 stopped,   0 zombie
%Cpu(s): 39.8 us, 57.0 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.3 hi,  2.9 si,  0.0 st
MiB Mem :   3732.0 total,     92.2 free,   3585.7 used,     54.1 buff/cache
MiB Swap:   4052.0 total,   3486.5 free,    565.5 used.      0.4 avail Mem 

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND                           
2361887 root      20   0 3984008   3.2g   1828 R  76.9  89.2   0:03.31 ksh                               
     52 root      20   0       0      0      0 R  19.9   0.0   0:16.51 kswapd0                           
      1 root      20   0  174936   5432   3144 S   0.0   0.1   0:03.24 systemd                           
      2 root      20   0       0      0      0 S   0.0   0.0   0:00.04 kthreadd
  • Component
  • ksh

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