Linux NFS client kernel tunable settings
September 18, 2007
We had a serious (lack of) performance issue today with a Linux NFS client machine, so I spent some time delving into the underdocumented world of kernel parameters that affect the Linux NFS client (not the NFS server, which has better documented stuff).
(I am going to use
The major tunable is
Unfortunately existing RPC connections are not resized if you change the number of slot table entries.
Contrary to what you might read in various places, changing
(This does mean that if you set a high slot table size and mount from a lot of different NFS servers, you could possibly use up a decent amount of kernel memory with socket send buffers.)
If you are doing NFS over UDP, as we are for some fileservers, you may
want to check the value of
(I believe this is a global amount of memory, not per connection or per fileserver, so it is safe to set it to several megabytes.)
It's possible that you will also want to increase
(It is a per-CPU queue limit, but you can't be sure that all of your network packet receive interrupts won't wind up being handled by the same CPU in a multi-CPU system).
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