Metadata Operations Such as ls -l, du, or find are Slow

Symptom: When a directory exceeds 100,000 files, metadata operations such as ls -l, du, or find are slow.

Generally, ls -l against a File Storage directory with 100,000 files is expected to complete in <= 10 seconds. Directory size does not significantly affect File Storage write throughput. If you see read/write slowness, ensure that you are not using rsize and wsize NFS mount options with a value of less than 1048576. As a best practice, do not specify rsize and wsize mount options, leave them at their default value of 1048576.

Cause: Directory scanning operations like ls, du, find, and rsync on a directory containing 100,000 files takes longer in File Storage.

Solutions:

  1. Redistribute your files to subdirectories instead of storing a large volume of files in a single directory. We recommended using subdirectories to keep directory sizes under 100,000 files.

    Tip

    Keeping your directory sizes small by using subdirectories is a best practice for File Storage.
  2. Use ls -ld or stat instead of ls -l. These operations are much quicker on large directories than ls -l.

    For example:

    [opc@instance01 dd]$ time ls -l|wc -l
    401425
    real 0m39.786s
    user 0m4.389s
    sys 0m5.403s
    [opc@instance01 dd]$ time ls -ld
    drwxrwxr-x. 4 opc opc 401424 Apr 17 14:18 .
    real 0m0.009s
    user 0m0.001s
    sys 0m0.003s
    [opc@instance01 dd]$ time stat .|grep Size
      Size: 401424     Blocks: 785        IO Block: 32768  directory
    real 0m0.010s
    user 0m0.002s
    sys 0m0.003s
    [opc@instance01 dd]$
  3. In some cases, an NFS client issue could cause directory scanning operations to enter into a loop and lead to an increase in scanning time. This issue affected the following Oracle Linux versions:

    • Oracle Linux 6
    • Oracle Linux 7 with Unbreakable Enterprise Kernel (UEK) versions earlier than 4.14.35-1902.301.1

    If you use Oracle Linux 6, upgrade to Oracle Linux 7.

    Oracle Linux 7 users can run the uname -a command to check the version of UEK. If the UEK version is earlier than 4.14.35-1902.301.1, upgrade to a later kernel version. The patch addressing this behavior was made available on April 17, 2020 and can be installed with Oracle Ksplice.

    Oracle Ksplice lets you apply important security updates and other critical kernel updates without a reboot. Oracle Ksplice must be installed on the instance. After you install Ksplice, you can install available Ksplice patches. See Oracle Ksplice for instructions.

    After you install the patch, you can verify the effective kernel version. Ksplice uptrack doesn't change the output of the uname command. uname continues to reflect the version of the kernel the instance was booted into.

    Instead, use uptrack-uname to see what effective kernel your instance is running. uptrack-uname has the same format as uname and supports the common uname flags, including -r and -a.

    For example: 

    $ uptrack-uname -r
    4.14.35-1902.302.2.el7uek.x86_64
  4. Directory scanning operations invoke the READDIRPLUS NFS call which is expensive when the directory contains many files. Instances can disable READDIRPLUS calls by using the nordirplus option when mounting. To disable the READDIRPLUS NFS operations on the instance:

    1. Open a terminal window on the instance.
    2. Unmount the file system with the umount command. For example:

      sudo umount 10.x.x.x:/fs-export-path /mnt/yourmountpoint
    3. Remount the file system, and include the -o nordirplus option to disable READDIRPLUS. For example:

      sudo mount -o nordirplus 10.x.x.x:/fs-export-path /mnt/yourmountpoint