kern/131360: [nfs] poor scaling behavior of the NFS server under load

Martin Birgmeier martin at
Sat Feb 7 07:40:06 PST 2009

The following reply was made to PR kern/131360; it has been noted by GNATS.

From: Martin Birgmeier <martin at>
To: bug-followup at
Subject: Re: kern/131360: [nfs] poor scaling behavior of the NFS server under load
Date: Sat, 7 Feb 2009 16:31:21 +0100 (CET)

 I am now very sure that this is an interaction with pppoa, and it is
 also worse than I originally thought: it will even lead to failed NFS
 transactions for the client.
 Here is what I have:
 Machine A ('server', a mini home server) does the following:
   - connecting to the Internet using usermode ppp over pppoa over an
     Alcatel ADSL modem
   - NFS serving FreeBSD sources
 Machine B does the following:
   - Mounting the FreeBSD sources from A (using amd), under directory
   - Compiling the FreeBSD sources: make -j4 buildworld, such that the
     corresponding obj is local (via amd again)
 Especially in the first phase of the buildworld (clean, depend, obj),
 there is a lot of simultaneous NFS traffic from B to A. As soon as
 a download is started at A (going via pppoa, of course), the load on
 A rises to very high values (> 20 not uncommon).
 This may lead to B aborting the compile, it just did that with
 "directory not found".
 Both machines are running 7.1.0.
 No such problem happended when both were running 6.3.0.

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