Date: Tue, 21 Sep 1999 20:14:17 -0700 (PDT) From: Kip Macy <kip@lyris.com> To: Dag-Erling Smorgrav <des@flood.ping.uio.no> Cc: stable@FreeBSD.ORG Subject: Re: Out of mbuf clusters Message-ID: <Pine.SOL.4.05.9909212010090.16568-100000@luna> In-Reply-To: <xzpzoygnz70.fsf@flood.ping.uio.no>
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You are, as is so often the case, correct. The way you phrase your responses sometimes blinds me, and evidently others, to the complete circumstances. -Kip On 21 Sep 1999, Dag-Erling Smorgrav wrote: > Kip Macy <kip@lyris.com> writes: > > This is in no way a rant against FreeBSD, but rather a rant against the > > attitude that one needs to know about OS internals to run a lightweight > > server. > > Calling what he did to that box "running a lightweight server" is a > very very wide stretch of imagination. I haven't seen his CLONE > program and therefore can't speak with 100% assurance, but I've run > similar experiments against my own servers, so I think I'm entitled to > make an educated guess about the behaviour of CLONE. It simulates a > worst-case scenario for an IRC server: open hundreds of connections, > log on, join a channel, but don't consume the data the server sends. > This fills up the server's send queues and exhausts its mbuf pool. > Memory consumption is a quadratic function of the number of clones > (linear if you just connect without joining a channel). > > The worst thing about CLONE is that it's neither a realistic > simulation of normal everyday IRC traffic (because real IRC clients > consume data almost as soon as it is sent, and therefore do not fill > up the server's send queues), nor of a typical attack against an IRC > server (because a properly-configured IRC server does not allow a > large number of connections from the same host, nor does it allow the > send queues to fill up, and is therefore practically immune to this > kind of attack). > > This is what mbuf usage looks like on a real-world IRC server with > 1800 clients: > > root@irc ~# netstat -m > 2859/9376 mbufs in use: > 947 mbufs allocated to data > 1912 mbufs allocated to packet headers > 180/2466/8192 mbuf clusters in use (current/peak/max) > 6104 Kbytes allocated to network (11% in use) > 0 requests for memory denied > 0 requests for memory delayed > 0 calls to protocol drain routines > > DES > -- > Dag-Erling Smorgrav - des@flood.ping.uio.no > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-stable" in the body of the message > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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