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262292Re: smtpd processes congregating at the pub

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  • Stan Hoeppner
    Jan 29, 2010
      Wietse Venema put forth on 1/29/2010 6:15 AM:
      > Stan Hoeppner:
      >> Based on purely visual non-scientific observation (top), it seems my smtpd
      >> processes on my MX hang around much longer in (Debian) 2.5.5 than they did in
      >> (Debian) 2.3.8. In 2.3.8 Master seemed to build them and tear them down very
      >
      > Perhaps Debian changed this:
      > http://www.postfix.org/postconf.5.html#max_idle
      >
      > The Postfix default is 100s.

      Yes, I confirmed this on my system.

      > I don't really see why anyone would shorten this - that's a waste
      > of CPU cycles. In particular, stopping Postfix daemons after 10s
      > means that people don't have a clue about what they are doing.
      > The fact that it's now increased to 30s confirms my suspicion.

      Think of a lightly loaded (smtp connects/min) vanity domain server that
      functions as a Postfix MX with local delivery, a Dovecot IMAP, a
      Lighty+Roundcube, a Samba server, and a dns resolver serving local requests and
      one remote workstation. The system is also used interactively (via SSH/BASH)
      for a number of things including an occasional kernel compile. The machine only
      has 384MB of RAM. My smtp load is low enough that having an smtpd process or
      two hanging around for 100 seconds just wastes 13-18MB per smtpd of memory for
      80-90 of those 100 seconds. This system regularly goes 5 minutes or more
      between smtp connects. Sometimes two come in simultaneously, and I end up with
      two smtpd processes hanging around for 100 seconds, eating over 30MB RAM with no
      benefit. Thus, for me, it makes more sense to have the smtpd's exit as soon as
      possible to free up memory that can be (better) used for something else. Yes, I
      guess I'm a maniac. ;)

      In this scenario, with very infrequent smtpd reuse, do you still think I should
      let them idle for 100 seconds, or at all? From my perspective, that 18-30MB+
      can often be better utilized during that time.

      --
      Stan
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