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# mount 127.0.0.1:/tmp/nfs_dir /mnt -o rw,soft,timeo=1,retrans=1,vers=3
This option set is pretty strange. It seems likely that once you get to the larger file sizes, the server is taking longer than .1s to respond to a call. The retrans and soft settings here ensure that when that happens, the client just errors out without retrying the call.
Maybe you should retry this test with a set of options that's tailored for more resiliency?
Also, note that mounting over the loopback like this is a recipe for deadlocks when memory gets scarce...
(In reply to comment #2)
> # mount 127.0.0.1:/tmp/nfs_dir /mnt -o rw,soft,timeo=1,retrans=1,vers=3
>
> This option set is pretty strange. It seems likely that once you get to the
> larger file sizes, the server is taking longer than .1s to respond to a call.
> The retrans and soft settings here ensure that when that happens, the client
> just errors out without retrying the call.
>
> Maybe you should retry this test with a set of options that's tailored for more
> resiliency?
>
> Also, note that mounting over the loopback like this is a recipe for deadlocks
> when memory gets scarce...
Tried this test with command timeo 10s:
# mount 127.0.0.1:/tmp/nfs_dir /mnt -o rw,soft,timeo=100,retrans=2,vers=3
It works well. Only the write speed is not stable. It is from around 45MB/s to 3MB/s. And sometime we can see an obvious waiting while writing to the nfs.
Ok, thanks for confirming the problem with the mount options. At this point, I'm going to close this as NOTABUG.
If you want to work on performance problems you'll probably want to open a new bug. You'll need to reproduce those results on a supported configuration (not mounting over a loopback interface). You'll also need to quantify the performance issues you're seeing. If you can come up with a consistent reproducer then that would be helpful.