Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261766AbVDZUCw (ORCPT ); Tue, 26 Apr 2005 16:02:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261767AbVDZUCw (ORCPT ); Tue, 26 Apr 2005 16:02:52 -0400 Received: from rproxy.gmail.com ([64.233.170.205]:59602 "EHLO rproxy.gmail.com") by vger.kernel.org with ESMTP id S261766AbVDZUCF convert rfc822-to-8bit (ORCPT ); Tue, 26 Apr 2005 16:02:05 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=MRsmo306Fpr0SZTeFpQFUl87i61sFZZuoNKYlSNvnzaO0BD+Etd+q8FXpafdlUP+rSc4HGKoYTv/A0xjnP2Q8gXEPViZ9KhWvxZU1X6lESE81QquXC0ZkARhkTWb/wczOGbRBPw615ua/Oa0+tkPRcCgKehjSW/FtOSiLZT3tGc= Message-ID: Date: Tue, 26 Apr 2005 15:02:01 -0500 From: Dmitry Torokhov Reply-To: dtor_core@ameritech.net To: johnpol@2ka.mipt.ru Subject: Re: [1/1] connector/CBUS: new messaging subsystem. Revision number next. Cc: netdev@oss.sgi.com, Greg KH , Jamal Hadi Salim , Kay Sievers , Herbert Xu , James Morris , Guillaume Thouvenin , linux-kernel@vger.kernel.org, Andrew Morton , Thomas Graf , Jay Lan In-Reply-To: <20050426232812.0c7bb3a4@zanzibar.2ka.mipt.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Content-Disposition: inline References: <20050411125932.GA19538@uganda.factory.vocord.ru> <20050426203023.378e4831@zanzibar.2ka.mipt.ru> <20050426220713.7915e036@zanzibar.2ka.mipt.ru> <20050426223126.37b7aea1@zanzibar.2ka.mipt.ru> <20050426224833.3b6a0792@zanzibar.2ka.mipt.ru> <20050426232812.0c7bb3a4@zanzibar.2ka.mipt.ru> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2353 Lines: 52 On 4/26/05, Evgeniy Polyakov wrote: > On Tue, 26 Apr 2005 14:06:36 -0500 > Dmitry Torokhov wrote: > > > On 4/26/05, Evgeniy Polyakov wrote: > > > On Tue, 26 Apr 2005 13:42:10 -0500 > > > Dmitry Torokhov wrote: > > > > Yes, that woudl work, although I would urge you to implement a message > > > > queue for callbacks (probably limit it to 1000 messages or so) to > > > > allow bursting. > > > > > > It already exist, btw, but not exactly in that way - > > > we have skb queue, which can not be filled from userspace > > > if pressure is so strong so work queue can not be scheduled. > > > It is of course different and is influenced by other things > > > but it handles bursts quite well - it was tested on both > > > SMP and UP machines with continuous flows of forks with > > > shape addon of new running tasks [both fith fork bomb and not], > > > so I think it can be called real bursty test. > > > > > > > Ok, hear me out and tell me where I am wrong: > > > > By default a socket can receive at least 128 skbs with 258-byte > > payload, correct? That means that user of cn_netlink_send, if started > > "fresh", 128 average - size connector messages. If sender does not > > want to wait for anything (unlike your fork tests that do schedule) > > that means that 127 of those 128 messages will be dropped, although > > netlink would deliver them in time just fine. > > > > What am I missing? > > Concider netlink_broadcast - it delivers skb to the kernel > listener directly to the input callback - no queueing actually, Right, no queueing for in-kernel... But then we have the following: netlink will drop messages sent to in-kernel socket ony if it can not copy skb - which is i'd say a very rare scenario. Connector, on the other hand, is guaranteed to drop all but the very first message sent between 2 schedules. That makes connector several orders of magnitude less reliable than bare netlink protocol. And you don't see it with your fork tests because you do schedule when you fork. -- Dmitry - 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/