From owner-freebsd-arch Mon Mar 24 20:53:36 2003 Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 55CF337B401; Mon, 24 Mar 2003 20:53:33 -0800 (PST) Received: from smtp2.server.rpi.edu (smtp2.server.rpi.edu [128.113.2.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id 05DF843F3F; Mon, 24 Mar 2003 20:53:32 -0800 (PST) (envelope-from drosih@rpi.edu) Received: from [128.113.24.47] (gilead.netel.rpi.edu [128.113.24.47]) by smtp2.server.rpi.edu (8.12.8/8.12.7) with ESMTP id h2P4rUn6014574; Mon, 24 Mar 2003 23:53:30 -0500 Mime-Version: 1.0 X-Sender: drosih@mail.rpi.edu Message-Id: In-Reply-To: <200303241752.40245.wes@softweyr.com> References: <200303241752.40245.wes@softweyr.com> Date: Mon, 24 Mar 2003 23:53:29 -0500 To: Wes Peters , John Baldwin From: Garance A Drosihn Subject: Re: Patch to protect process from pageout killing Cc: freebsd-arch@FreeBSD.ORG Content-Type: text/plain; charset="us-ascii" ; format="flowed" X-Scanned-By: MIMEDefang 2.28 X-Spam-Status: No, hits=-25.3 required=5.0 tests=AWL,EMAIL_ATTRIBUTION,IN_REP_TO,QUOTED_EMAIL_TEXT, REFERENCES,REPLY_WITH_QUOTES autolearn=ham version=2.50 X-Spam-Level: X-Spam-Checker-Version: SpamAssassin 2.50 (1.173-2003-02-20-exp) Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG At 5:52 PM -0800 3/24/03, Wes Peters wrote: >On Monday 24 March 2003 11:09, John Baldwin wrote: > > I think that adopting the SIGDANGER approach would be better > > rather than rolling our own private interface. > >It's not clear to me the SIGDANGER interface allows me to say >"go elsewhere bub, I'm really important." In this case, that >is essential. I think even in the general FreeBSD case you can >make a point for a setting like this in, say, named. Please check out the descriptions I posted previously. SIGDANGER (as implemented by AIX) explicitly provides two things. The process gets to decide which one they (the process) wants: 1) signal me at the first sign of trouble, and I'll free up some virtual memory (possibly by exit()-ing). 2) do not ever kill me to free up memory. I think that we could improve upon the AIX implementation if we wanted to, but I think people are so used to having problems with AIX that they hate the idea of SIGDANGER as soon as they see the letters AIX. Having used AIX for more than ten years now, I can sympathize with that, but in the specific case of SIGDANGER there is an idea that can work quite well. (reference on sigdanger was at: http://nscp.upenn.edu/aix4.3html/aixbman/baseadmn/pag_space_under.htm ) >The SIGDANGER interface worries me in general, partly because it's >a signal and partly because it complicates the design of EVERYTHING >just to handle it. I guess a lot depends on the implementation >details of how SIGDANGER and the default handlers are designed, >but nothing I saw last week gave me a warm fuzzy about that. I don't know enough about the lower-level implementation details, but I did think the recent discussion on the src-committers list did include a number of good ideas. I am horribly over-committed with things that I've promised to do (including stuff for my real- world job...), so I can't look into SIGDANGER ideas right now, but I'm more than happy to try to explain how it should work. -- Garance Alistair Drosehn = gad@gilead.netel.rpi.edu Senior Systems Programmer or gad@freebsd.org Rensselaer Polytechnic Institute or drosih@rpi.edu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message