From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [MM PATCH V4.1 5/6] slub: support for bulk free with SLUB freelists Date: Wed, 7 Oct 2015 12:39:19 +0200 Message-ID: <20151007123919.27a9c823@redhat.com> References: <560ABE86.9050508@gmail.com> <20150930114255.13505.2618.stgit@canyon> <20151001151015.c59a1360c7720a257f655578@linux-foundation.org> <20151002114118.75aae2f9@redhat.com> <20151002154039.69f82bdc@redhat.com> <20151002145044.781c911ea98e3ea74ae5cf3b@linux-foundation.org> <20151005212639.35932b6c@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-mm@kvack.org, Christoph Lameter , Alexander Duyck , netdev@vger.kernel.org, Arnaldo Carvalho de Melo , brouer@redhat.com To: Andrew Morton Return-path: Received: from mx1.redhat.com ([209.132.183.28]:42471 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750916AbbJGKjX (ORCPT ); Wed, 7 Oct 2015 06:39:23 -0400 In-Reply-To: <20151005212639.35932b6c@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 5 Oct 2015 21:26:39 +0200 Jesper Dangaard Brouer wrote: > On Fri, 2 Oct 2015 14:50:44 -0700 Andrew Morton wrote: > [...] > > > Deleting the BUG altogether sounds the best solution. As long as the > > kernel crashes in some manner, we'll be able to work out what happened. > > And it's cant-happen anyway, isn't it? > > To me WARN_ON() seems like a good "documentation" if it does not hurt > performance. I don't think removing the WARN_ON() will improve > performance, but I'm willing to actually test if it matters. I tested removing BUG/WARN_ON altogether, and it gives slightly worse performance. The icache-misses only increase approx 14% (not 112% as before). This, I'm willing to attribute to some code alignment issue. Thus, let us just keep the WARN_ON() and move along. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer