Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261317AbUC3Vai (ORCPT ); Tue, 30 Mar 2004 16:30:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261262AbUC3Vai (ORCPT ); Tue, 30 Mar 2004 16:30:38 -0500 Received: from mail1.slu.se ([130.238.96.11]:63688 "EHLO mail1.slu.se") by vger.kernel.org with ESMTP id S261317AbUC3Vac (ORCPT ); Tue, 30 Mar 2004 16:30:32 -0500 From: Robert Olsson MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16489.59080.303710.986410@robur.slu.se> Date: Tue, 30 Mar 2004 23:29:44 +0200 To: Andrea Arcangeli Cc: Dipankar Sarma , linux-kernel@vger.kernel.org, netdev@oss.sgi.com, Robert Olsson , "Paul E. McKenney" , Dave Miller , Alexey Kuznetsov , Andrew Morton Subject: Re: route cache DoS testing and softirqs In-Reply-To: <20040330204731.GG3808@dualathlon.random> References: <20040329184550.GA4540@in.ibm.com> <20040329222926.GF3808@dualathlon.random> <20040330144324.GA3778@in.ibm.com> <20040330195315.GB3773@in.ibm.com> <20040330204731.GG3808@dualathlon.random> X-Mailer: VM 7.17 under Emacs 21.3.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1247 Lines: 30 Andrea Arcangeli writes: > I see what's going on now, yes my patch cannot help. the workload is > simply generating too much hardirq load, and it's like if we don't use > softirq at all but that we process the packet inside the hardirq for > this matter. As far as RCU is concerned it's like if there a no softirq > at all but that we process everything in the hardirq. > > so what you're looking after is a new feature then: > > 1) rate limit the hardirqs > 2) rate limit only part of the irq load (i.e. the softirq, that's handy > since it's already splitted out) to scheduler-aware context (not > inside irq context anymore) > 3) stop processing packets in irqs in the first place (NAPI or similar) Hello! No Andrea it pure softirq workload. Interfaces runs with irq disabled at this load w. NAPI. Softirq's are run from spin_unlock_bh etc when doing route lookup and GC. And the more fine-grained locking we do the the more do_softirq's are run. Cheers. --ro - 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/