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Date:      Mon, 7 Aug 2000 17:08:01 -0400 (EDT)
From:      Robert Watson <rwatson@freebsd.org>
To:        Dennis <dennis@etinc.com>
Cc:        hackers@freebsd.org
Subject:   Re: FreeBSD belly up with big config
Message-ID:  <Pine.NEB.3.96L.1000807170600.3282A-100000@fledge.watson.org>
In-Reply-To: <200008051708.NAA00486@etinc.com>

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On Sat, 5 Aug 2000, Dennis wrote:

> With 1800 interfaces in the system Freebsd seems to use about 50Mhz of cpu
> when idle in "interrupts" even when there are no interrupts to process. on
> a 500Mhz box it uses 10% of the cpu and it seems linear with different
> speed processors.
> 
> the 1800 interfaces are 900 DLCIs on a T3 frame with 900 bridge groups
> (rather common for a DSL delivered via Frame). This with just one
> line...the same problem could occur with say 8 T1 lines with 100+ DLCIs on
> each.
> 
> It seems that there is substantial overhead just scanning interfaces for
> some routine maintenance...is there any hope of alleviating this deboggle?

I'd made some similar observations about the current lack of scalability
both in management of (struct ifnet) chains, and mountpoints in the file
system.  As we move to a more dynamic network environment, a lot of things
about ifnet handling need to be improved, including fixing (really fixing)
the freeing of struct ifnet (lots of loose mbuf pointers hanging around to
the struct ifnet, as well as stuff in filtering rules, et al).  The
bridging code isn't currently designed to work in this manner, and also
has problems with dynamically introduced interfaces (try and use options
BRIDGE and the sysctl enabled with a pccard sometime).

  Robert N M Watson 

robert@fledge.watson.org              http://www.watson.org/~robert/
PGP key fingerprint: AF B5 5F FF A6 4A 79 37  ED 5F 55 E9 58 04 6A B1
TIS Labs at Network Associates, Safeport Network Services



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