Re: performance of jailed processes

From: Eirik Oeverby (ltning_at_anduin.net)
Date: 03/30/04

  • Next message: Colin Percival: "Re: Small typo in the setproctitle() output in sbin/fsck_ffs/pass5.c" 
    Date: Tue, 30 Mar 2004 22:22:32 +0200
To: Dag-Erling Smørgrav <des@des.no>

    Hi there,

    and I thought I was using jails on a 'big' scale... 400 jails on one
    single box, that's pretty amazing! What kind of jails are these, i.e.
    what are they used for? Encapsulating single processes/tasks only, or
    more complex things too? And what hardware are you on, CPU and memory-wise?

    /Eirik

    Dag-Erling Smørgrav wrote:
    > 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.
    >
    >
    > 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
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  • Next message: Colin Percival: "Re: Small typo in the setproctitle() output in sbin/fsck_ffs/pass5.c"

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