NFS on 10G interface terribly slow

Gerrit Kühn gerrit.kuehn at
Fri Jun 26 09:59:56 UTC 2015

On Thu, 25 Jun 2015 20:49:11 -0400 (EDT) Rick Macklem
<rmacklem at> wrote about Re: NFS on 10G interface terribly slow:

RM> Recent commits to stable/10 (not in 10.1) done by Alexander Motin
RM> (mav@) might help w.r.t. write performance (it avoids large writes
RM> doing synchronous writes when the wcommitsize is exceeded). If you can
RM> try stable/10, that might be worth it.

Ok, I'll schedule an update then, I guess. OTOH, Scott reported that a
similar setup is working fine for him with 10.0 and 10.1, so there is
probably not much to gain. I'll try anyway...

RM> Otherwise, the main mount option you can try is "wcommitsize", which
RM> you probably want to make larger.

Hm, which size would you recommend? I cannot find anything about this
setting, not even what the default value would be. Is this reflected in
some sysctl, or how can I find out what the actual value is?


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