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  1. RHEL
  2. RHEL-5099

Slow ssh connection when using password authentication due to a large amount of "close" syscall

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    • rhel-9.4
    • rhel-9.0.0
    • pam
    • pam-1.5.1-16.el9
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    • Important
    • rhel-sst-idm-sssd
    • ssg_idm
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      Description of problem:
      Connecting via ssh to a server with a password is longer with RHEL 9 compared to RHEL 8

      IT seemed to be resolved in RHEL 8 with the patch pam-1.3.1-fds-closing.patch (RHBZ1737812), but the fix has been reverted upstream and is not part of the code anymore.

      Version-Release number of selected component (if applicable):
      9.0, 9.1 and 9.2

      How reproducible:
      Connect using a password authentication

      Actual results:
      With RHEL 9, sshd spends 25% of its time running the close syscall :
      RHEL 9 :
      % time seconds usecs/call calls errors syscall
      ------ ----------- ----------- --------- --------- ----------------
      71.81 1.680497 35755 47 21 wait4
      25.48 0.596416 4 131894 131057 close
      0.48 0.011248 11 979 335 openat
      0.31 0.007196 359 20 execve
      ...

      RHEL 8 :
      % time seconds usecs/call calls errors syscall
      ------ ----------- ----------- --------- --------- ----------------
      81.89 0.099364 1505 66 31 wait4
      2.64 0.003209 4 773 208 openat
      2.53 0.003064 139 22 execve
      2.26 0.002739 80 34 clone
      1.21 0.001467 27 53 socket
      1.09 0.001328 16 80 3 write
      1.04 0.001260 2 493 2 read
      0.90 0.001094 2 495 mmap

      Is it possible to recreate a patch to correct this behavior?

              ipedrosa@redhat.com Iker Pedrosa
              rhn-support-nbourgeo Nicolas Bourgeois
              Iker Pedrosa Iker Pedrosa
              SSSD QE SSSD QE
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                Created:
                Updated:
                Resolved: