From owner-freebsd-arch Wed Nov 8 14:57:23 2000 Delivered-To: freebsd-arch@freebsd.org Received: from erouter0.it-datacntr.louisville.edu (erouter0.it-datacntr.louisville.edu [136.165.1.36]) by hub.freebsd.org (Postfix) with ESMTP id 4AA6537B479 for ; Wed, 8 Nov 2000 14:57:15 -0800 (PST) Received: from osaka.louisville.edu (osaka.louisville.edu [136.165.1.114]) by erouter0.it-datacntr.louisville.edu (Postfix) with ESMTP id 49DCE25360; Wed, 8 Nov 2000 17:57:09 -0500 (EST) Received: by osaka.louisville.edu (Postfix, from userid 15) id 6F3F01861D; Wed, 8 Nov 2000 17:57:04 -0500 (EST) Date: Wed, 8 Nov 2000 17:57:04 -0500 From: Keith Stevenson To: Terry Lambert Cc: "Daniel C. Sobral" , arch@FreeBSD.ORG Subject: AIX SIGDANGER (was Re: softdep panic due to blocked malloc) Message-ID: <20001108175704.B1405@osaka.louisville.edu> References: <3A09346F.7543C1DD@newsguy.com> <200011081817.LAA21138@usr08.primenet.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <200011081817.LAA21138@usr08.primenet.com>; from tlambert@primenet.com on Wed, Nov 08, 2000 at 06:17:14PM +0000 Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG This is a bit offtopic, but I couldn't help myself. (I'm an AIX admin) Quoting IBM's July 2000 system documentation CDROM: The system monitors the number of free paging space blocks and detects when a paging-space shortage exists. When the number of free paging-space blocks falls below a threshold known as the paging-space warning level, the system informs all processes (except kprocs) of this condition by sending the SIGDANGER signal. If the shortage continues and falls below a second threshold known as the paging-space kill level, the system sends the SIGKILL signal to processes that are the major users of paging space and that do not have a signal handler for the SIGDANGER signal (the default action for the SIGDANGER signal is to ignore the signal). The system continues sending SIGKILL signals until the number of free paging-space blocks is above the paging-space kill level. So, SIGDANGER doesn't buy you much unless your applications have a handler for it. (In my experience, most don't.) I was not very happy when I hit a low memory situation and AIX started committing random acts of violence against my process table. The system ended up being so hosed, I had to reboot to maintenance mode and repair a bunch of datafiles. (One of our production applications doesn't SIGKILL gracefully.) I think that SIGDANGER would make a lot more sense if its default action was the same as SIGTERM. SIGKILL'ing everything in sight isn't a lot cleaner (IMO) than letting the system crash. Regards, --Keith Stevenson-- -- Keith Stevenson System Programmer - Data Center Services - University of Louisville keith.stevenson@louisville.edu GPG key fingerprint = 332D 97F0 6321 F00F 8EE7 2D44 00D8 F384 75BB 89AE On Wed, Nov 08, 2000 at 06:17:14PM +0000, Terry Lambert wrote: > > > I haven't seen an occurrance of one in nature (well, AIX) in at > > > least 5 years. > > > > I did... :-( > > And wished the damned application knew about the signal and stopped > > hogging memory. > > ??? > > It's my experience that if you don't trap the thing, you > terminate. Did your application ignore the thing when you > didn't want it to, or did it terminate, when you didn't want > want it to? To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message