NFS: slow to open files (recent regression?)

Hi all,

I’ve been using my Omnia as an NFS server for several months. In the last week or two, something changed and the performance became really bad. Specifically, it often takes 30 sec to simply open a file. Listing directories is fine, and reading the file is fine once it’s open. It’s just the open() system call that takes 30 sec. Here are some random facts about this:

  • the open() call does succeed, it just takes 30 sec
  • once a particular file has been opened, it stays fine … for a while (client-side cache?)
  • after opening one file, other files in that directory appear to be OK … for a while
  • but if I pick files at random scattered around the NFS share, opening a new one is almost always slow
  • if I wait a few minutes and try re-open the same file, or files in the same directory, they’re slow again
  • if I mount with nfsvers=3 to revert to NFSv3, it’s fine
  • I have lots of strace output and tcpdump output to show that 1) it’s just opening the file and 2) it is almost exactly 30 sec, every time

Any clue what’s going on here? Is this a known bug? Is there a better workaround than downgrading to NFSv3?



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