Date: Tue, 30 Mar 2004 21:09:35 +0200 From: des@des.no (Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?=) To: Robert Watson <rwatson@freebsd.org> Cc: current@freebsd.org Subject: Re: performance of jailed processes Message-ID: <xzpbrmenocw.fsf@dwp.des.no> In-Reply-To: <Pine.NEB.3.96L.1040330133811.93169H-100000@fledge.watson.org> (Robert Watson's message of "Tue, 30 Mar 2004 13:45:24 -0500 (EST)") References: <Pine.NEB.3.96L.1040330133811.93169H-100000@fledge.watson.org>
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Robert Watson <rwatson@freebsd.org> writes: > - DNS -- I know you mentioned it, but I'd check anyway. Especially if > resolv.conf has bad DNS servers in it in the jails, etc. You might try > writing a trivial gethostbyname() test app and timing it in and out of > the jail. Also look at the reverse lookup done by the MySQL server. > The impact of the source IP address might be particularly interesting. Packet traces already show that there is no delay between query and reply, the reply just takes a long time to transmit. > - It would be interesting to know if applications outside the jail bound > to various IP addresses see performance differences depending on the IP > used. We have hashed IP address lookup, but there are some operations > in the stack that require walking the list of addresses, etc. If the > non-jailed software always uses the first address because they're all in > the same subnet, that might conceivably make a difference. Taking jail > out of the picture in some basic micro-benchmarks might help here also.= =20 Non-jailed software always uses the first IP address, which is in its own subnet. The jails draw from a pool of ~1000 IP addresses on the same interface, but in a different subnet. The jail I've been testing in is about a quarter of the way down the list. > Can you identify any micro-benchmarks rather than macro-benchmarks that > reflect a significant difference? haven't had much luck with that... fetch, for instance, doesn't seem to suffer, but with mysql the difference is dramatic: (outside jail) 1 row in set (0.01 sec) (inside jail) 1 row in set (13.20 sec) note that 13 seconds is far too short for a DNS issue, and that the time reported is measured *after* login (i.e. after any DNS lookup) DES --=20 Dag-Erling Sm=F8rgrav - des@des.no
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