From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756482Ab2B1Hng (ORCPT ); Tue, 28 Feb 2012 02:43:36 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:49985 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750780Ab2B1Hnf (ORCPT ); Tue, 28 Feb 2012 02:43:35 -0500 Date: Mon, 27 Feb 2012 23:44:51 -0800 From: Andrew Morton To: "Jan Beulich" Cc: Subject: Re: [PATCH v2] consolidate WARN_...ONCE() static variables Message-Id: <20120227234451.3a00a76a.akpm@linux-foundation.org> In-Reply-To: <4F4C93520200007800075197@nat28.tlf.novell.com> References: <4F4BAAFA0200007800074F8F@nat28.tlf.novell.com> <20120227160302.ef9f6af4.akpm@linux-foundation.org> <4F4C93520200007800075197@nat28.tlf.novell.com> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 28 Feb 2012 07:41:54 +0000 "Jan Beulich" wrote: > >>> On 28.02.12 at 01:03, Andrew Morton wrote: > > On Mon, 27 Feb 2012 15:10:34 +0000 > > "Jan Beulich" wrote: > > > >> Due to the alignment of following variables, these typically consume > >> more than just the single byte that 'bool' requires, and as there are > >> a few hundred instances, the cache pollution (not so much the waste of > >> memory) sums up. Put these variables into their own section, outside > >> of any half way frequently used memory range. > >> > >> v2: Do the same also to the __warned variable of rcu_lockdep_assert(). > >> (Don't, however, include the ones used by printk_once() and alike, as > >> they can potentially be hot.) > > > > I have a bad feeling that I still don't understand this patch. Ho hum. > > > > What are the rules for the new .data.unlikely section? When should > > people put variables into this section? Perhaps we can document this > > somewhere? > > If I knew the "where" part of this, I could put together a few sentences. > I just grep-ed through Documentation/, without finding e.g. any rules > or guidelines for using {,un}likely()... > At the definition site in vmlinux.lds?