Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261797AbUCaHiQ (ORCPT ); Wed, 31 Mar 2004 02:38:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261798AbUCaHiQ (ORCPT ); Wed, 31 Mar 2004 02:38:16 -0500 Received: from e34.co.us.ibm.com ([32.97.110.132]:48073 "EHLO e34.co.us.ibm.com") by vger.kernel.org with ESMTP id S261797AbUCaHiO (ORCPT ); Wed, 31 Mar 2004 02:38:14 -0500 Date: Wed, 31 Mar 2004 13:06:30 +0530 From: Dipankar Sarma To: Robert Olsson Cc: Andrea Arcangeli , linux-kernel@vger.kernel.org, netdev@oss.sgi.com, "Paul E. McKenney" , Dave Miller , Alexey Kuznetsov , Andrew Morton Subject: Re: route cache DoS testing and softirqs Message-ID: <20040331073630.GA3681@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20040329184550.GA4540@in.ibm.com> <20040329222926.GF3808@dualathlon.random> <20040330144324.GA3778@in.ibm.com> <20040330195315.GB3773@in.ibm.com> <20040330204731.GG3808@dualathlon.random> <16489.59080.303710.986410@robur.slu.se> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <16489.59080.303710.986410@robur.slu.se> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1456 Lines: 31 On Tue, Mar 30, 2004 at 11:29:44PM +0200, Robert Olsson wrote: > 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) > > 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. Not lookup, we don't take the lock in lookup. Probably route insertions which will happen very frequently in this case. Thanks Dipankar - 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/