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From: CHOI Junho <cjh@kr.FreeBSD.org>
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cc: freebsd-performance@freebsd.org
Subject: mbuf tuning
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Hi,

What is general guidelines of mbuf cluster tunables? I usually use

kern.ipc.nmbclusters="65536"

in /boot/loader.conf.local. But it has limits on concurrent TCP
sessions, under my /etc/sysctl.conf configuration:

net.inet.tcp.sendspace=65536
net.inet.tcp.recvspace=65536

With above parameters, about 1000 connection was the maximum. Of course
if I set 1/2 value for tcp buffer(32768), maximum connection is
doubled. But I want more.

Increasing kern.ipc.nmbclusters caused frequent kernel panic
under 4.7/4.8/4.9. How can I set more nmbclusters value with 64K tcp
buffers? Or is any dependency for mbufclusters value? (e.g. RAM size,
kern.maxusers value or etc)

p.s. RAM is 2G, Xeon 2.0G x 1 or 2 machines.

--
CHOI Junho <http://www.kr.FreeBSD.org/~cjh>     KFUG <cjh at kr.FreeBSD.org>
FreeBSD Project <cjh at FreeBSD.org>        Web Data Bank <cjh at wdb.co.kr>
Key fingerprint = 1369 7374 A45F F41A F3C0  07E3 4A01 C020 E602 60F5