Date: Wed, 20 Mar 2002 17:43:29 +0100 From: Francesco Casadei <fcasadei@inwind.it> To: Dmitry Mottl <dima@sinp.msu.ru> Cc: freebsd-questions@FreeBSD.org Subject: Re: mbufs, nmbclusters Message-ID: <20020320174329.E2375@goku.kasby> In-Reply-To: <Pine.BSF.4.43.0203181801540.59799-100000@BigKing.sinp.msu.ru>; from dima@sinp.msu.ru on Mon, Mar 18, 2002 at 06:14:23PM %2B0300 References: <Pine.BSF.4.43.0203181801540.59799-100000@BigKing.sinp.msu.ru>
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On Mon, Mar 18, 2002 at 06:14:23PM +0300, Dmitry Mottl wrote:
> Hi
>=20
> How can I find which program uses a lot of kernel mbufs and nmbclusters?
> Is the maximum number of nmbclusters that can be occupied by program is
> N*(net.inet.tcp.sendspace+net.inet.tcp.recvspace)/2048, where N is number
> of tcp connections opened by the program?
>=20
> Thank you
>=20
> Best regards,
> Dmitry Mottl
>=20
>=20
> To Unsubscribe: send mail to majordomo@FreeBSD.org
> with "unsubscribe freebsd-questions" in the body of the message
>=20
> end of the original message
=46rom tuning(7) manual page:
[...]
kern.ipc.nmbclusters may be adjusted to increase the number of network
mbufs the system is willing to allocate. Each cluster represents appr=
ox=AD
imately 2K of memory, so a value of 1024 represents 2M of kernel memory
reserved for network buffers. You can do a simple calculation to figu=
re
out how many you need. If you have a web server which maxes out at 10=
00
simultaneous connections, and each connection eats a 16K receive and 1=
6K
send buffer, you need approximate 32MB worth of network buffers to deal
with it. A good rule of thumb is to multiply by 2, so 32MBx2 =3D 64MB=
/2K =3D
32768. So for this case you would want to set kern.ipc.nmbclusters to
32768. We recommend values between 1024 and 4096 for machines with mo=
d=AD
erates amount of memory, and between 4096 and 32768 for machines with
greater amounts of memory. Under no circumstances should you specify =
an
arbitrarily high value for this parameter, it could lead to a boot-time
crash. The -m option to netstat(1) may be used to observe network clu=
s=AD
ter use. Older versions of FreeBSD do not have this tunable and requi=
re
that the kernel config(8) option NMBCLUSTERS be set instead.
[...]
So I would say yes the number of nmbclusters is:
N*(net.inet.tcp.sendspace+net.inet.tcp.recvspace)/2048
Francesco Casadei
--=20
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