Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161071AbVLOIfu (ORCPT ); Thu, 15 Dec 2005 03:35:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161072AbVLOIfu (ORCPT ); Thu, 15 Dec 2005 03:35:50 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:53429 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1161071AbVLOIft (ORCPT ); Thu, 15 Dec 2005 03:35:49 -0500 Subject: Re: [RFC][PATCH 0/3] TCP/IP Critical socket communication mechanism From: Arjan van de Ven To: "David S. Miller" Cc: sri@us.ibm.com, mpm@selenic.com, ak@suse.de, linux-kernel@vger.kernel.org, netdev@vger.kernel.org In-Reply-To: <20051215.002120.133621586.davem@davemloft.net> References: <20051215033937.GC11856@waste.org> <20051214.203023.129054759.davem@davemloft.net> <20051215.002120.133621586.davem@davemloft.net> Content-Type: text/plain Date: Thu, 15 Dec 2005 09:35:20 +0100 Message-Id: <1134635721.16486.7.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-Spam-Score: -2.8 (--) X-Spam-Report: SpamAssassin version 3.0.4 on pentafluge.infradead.org summary: Content analysis details: (-2.8 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.8 ALL_TRUSTED Did not pass through any untrusted hosts X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1701 Lines: 36 On Thu, 2005-12-15 at 00:21 -0800, David S. Miller wrote: > From: Sridhar Samudrala > Date: Wed, 14 Dec 2005 23:37:37 -0800 (PST) > > > Instead, you seem to be suggesting in_emergency to be set dynamically > > when we are about to run out of ATOMIC memory. Is this right? > > Not when we run out, but rather when we reach some low water mark, the > "critical sockets" would still use GFP_ATOMIC memory but only > "critical sockets" would be allowed to do so. > > But even this has faults, consider the IPSEC scenerio I mentioned, and > this applies to any kind of encapsulation actually, even simple > tunneling examples can be concocted which make the "critical socket" > idea fail. > > The knee jerk reaction is "mark IPSEC's sockets critical, and mark the > tunneling allocations critical, and... and..." well you have > GFP_ATOMIC then my friend. > > In short, these "seperate page pool" and "critical socket" ideas do > not work and we need a different solution, I'm sorry folks spent so > much time on them, but they are heavily flawed. maybe it should be approached from the other side; having a way to mark connections as low priority (say incoming http connections to your webserver) or as non-critical/expendable would give the "normal" GFP_ATOMIC ones a better chance in case of overload/DDOS etc. It's not going to solve the VM deadlock issue wrt iscsi/nfs; however it might be useful in the "survive slashdot" sense... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/