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Date:      Mon, 9 Nov 1998 09:10:09 -0800 (PST)
From:      Archie Cobbs <archie@whistle.com>
To:        current@FreeBSD.ORG
Subject:   Re: The infamous dying daemons bug
Message-ID:  <199811091710.JAA01978@bubba.whistle.com>
In-Reply-To: <199811091626.IAA21393@hub.freebsd.org> from "garman@earthling.net" at "Nov 9, 98 11:28:08 am"

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garman@earthling.net writes:
> > Totally unrelated to the problem.  It seems, so far as I was able to
> > characterize, to happen to daemons which are *swapped out* at the time
> > of the memory shortage.  If it's active enough to still be in core, it
> > doesn't get spammed.
> > 
> Yes, this fits the symptoms i'm seeing here with samba.  The daemon
> will be fine as long as it has not been swapped out; after that, it's
> *poof*.  That's also probably why people with heavy-use samba servers
> haven't seen this problem.

Vague observations..

 - samba, inetd, sendmail all do a lot of forking (which
   may be nothing other than a common need for more memory)

 - samba uses memory mapping to implement file locking

I'd like to try to confirm/deny that memory mapping is one
required ingredient of the recipie. The only other known
ingredient seems to be running out of swap.

Could someone who is seeing this happen often recompile their
kernel with memory mapping disabled, and see if that changes
anything (other than making programs that use mmap() stop working)?
Ie, comment out

  options         SYSVSHM     
  options         SYSVSEM
  options         SYSVMSG     

(this *does* disable mmap(), right? If not, instead patch the
mmap() syscall to always return an error)

-Archie

___________________________________________________________________________
Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com

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