[LU-18448] Read Directory page on open.

• Type: Improvement
• Resolution: Unresolved
• Priority: Major
• Fix Version/s: Lustre 2.17.0
• Severity: 3
• Assignee: Alexey Lyashkov
• Reporter: Alexey Lyashkov

Description

DoM provide a way to readahead for the pages on MDT, it save a time and rpc for MDT.
Directory want to have similar option. It's very useful for small directories and increase a readdir speed for tree walk.

100k directories with 100 files on each.

1. find /mnt/kjlmo2/tests_dir -type d | wc -l
   102731

unpatched.
[root@c-lmo1005 ~]# time /bin/ls -1R /mnt/kjlmo2/tests_dir >& /dev/null
real 1m48.603s

patched
[root@c-lmo1004 ~]# time /bin/ls -1R /mnt/kjlmo2/tests_dir >& /dev/null
real 1m9.564s