kern.ipc.nsfbufs Max Value?

Holtor holtor at
Sun Dec 10 08:23:02 PST 2006

I have an extremely busy web server here serving mostly static html pages
and images using apache 2.2.3 with sendfile enabled. It's a Dual Xeon
server with 4 GB RAM and I've tweaked many sysctl variables to help the
system chug along. At peak, apache is running nearly 1,500 child

To my question, what is the max value of kern.ipc.nsfbufs and does it
depend on any other values? I had originally increased it to 32768 however
sfbufs got maxed out slowing the server. Then I increased it to 65536 and
currently have these results:

45348/48844/65536 sfbufs in use (current/peak/max)

To me that's too close for comfort so I further tried to increase it to
131072 however with that setting the system would not boot. The kernel
page faulted with an error in the swapper process until I decreased
kern.ipc.nsfbufs back to 65536.

Is there anyway to increase this value even higher? The server has nearly
2.5 GB of free ram out of the 4 GB installed and the load averages are
very low 0.07, 0.15, 0.34 so hopefully it's possible to tweak this some

Any ideas?

Thank You,

Holt G.

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