Date: Tue, 10 Jul 2001 19:30:01 -0700 (PDT) From: Leo Bicknell <bicknell@ufp.org> To: freebsd-bugs@FreeBSD.org Subject: Re: conf/28882: Network defaults are absurdly low. Message-ID: <200107110230.f6B2U1178280@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
The following reply was made to PR conf/28882; it has been noted by GNATS.
From: Leo Bicknell <bicknell@ufp.org>
To: "Richard A. Steenbergen" <ras@e-gerbil.net>
Cc: Leo Bicknell <bicknell@ufp.org>,
FreeBSD-gnats-submit@freebsd.org, billf@elvis.mu.org
Subject: Re: conf/28882: Network defaults are absurdly low.
Date: Tue, 10 Jul 2001 22:27:32 -0400
Ah ha, I believe the reason I had no MBUF problems is because I had
raised a number of other defaults, which may be a good idea anyway.
Currently the number of MBUF's is dependant on the number of users,
which really makes no sense as the max number needed can be calculated
by the socket size.
It also shows a minor misunderstanding in my original suggestion. So
I will revise it. Rather than:
kern.ipc.maxsockbuf=16777216
net.inet.tcp.sendspace=4194304
net.inet.tcp.recvspace=4194304
I now suggest _defaults_ of:
kern.ipc.maxsockbuf=8388608
net.inet.tcp.sendspace=419430
net.inet.tcp.recvspace=419430
There was no reason to let the max get that big. Doing calculations
on the normal defaults (as those who write programs to exceed them are
on their own) we get a worst case need of 419430 / 256 or 1638 MBUF's
per connection. Considering a "busy" server is unlikely to exceed
100 connections open simultaneously (and the few news servers and irc
servers that exceed that are special cases, very few web servers or
general purpose boxes get to that number) 163800 MBUF's maximum would
be enough. Of course, if they were all allocated for some reason that
default would allow about 40 Meg of memory to be allocated to the
network, but then I think it's reasonable to assume that a machine
servicing 100 simultaneous connections has 40 Meg around to spare,
in the worst cases.
The defaults now are based on:
#define NMBCLUSTERS (512 + MAXUSERS * 16)
TUNABLE_INT_DECL("kern.ipc.nmbclusters", NMBCLUSTERS, nmbclusters);
TUNABLE_INT_DECL("kern.ipc.nmbufs", NMBCLUSTERS * 4, nmbufs);
So you get 32768 MBUF's today with maxusers at 512. So I'm suggesting
that number needs to be about 5x higher to make everything work
right.
In reality, I'm betting about 3x-4x would be the right number for
real world situations.
So, MBUF's need to be evaluated as well. As this is quickly getting
more complicated, I'll suggest that this pr might need to split. I
still believe the defaults need to be higher to help the end users
installing the system who don't know how to tune this stuff. I
also think perhaps a new section of the handbook or something needs
to address these issues in more detail with all the related gook
that needs to be changed.
--
Leo Bicknell - bicknell@ufp.org
Systems Engineer - Internetworking Engineer - CCIE 3440
Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-bugs" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200107110230.f6B2U1178280>