From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756628Ab2B1IQG (ORCPT ); Tue, 28 Feb 2012 03:16:06 -0500 Received: from nat28.tlf.novell.com ([130.57.49.28]:31949 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754255Ab2B1IQE convert rfc822-to-8bit (ORCPT ); Tue, 28 Feb 2012 03:16:04 -0500 Message-Id: <4F4C9B7802000078000751BC@nat28.tlf.novell.com> X-Mailer: Novell GroupWise Internet Agent 12.0.0 Date: Tue, 28 Feb 2012 08:16:40 +0000 From: "Jan Beulich" To: "Andrew Morton" Cc: Subject: Re: [PATCH v2] consolidate WARN_...ONCE() static variables References: <4F4BAAFA0200007800074F8F@nat28.tlf.novell.com> <20120227160302.ef9f6af4.akpm@linux-foundation.org> <4F4C93520200007800075197@nat28.tlf.novell.com> <20120227234451.3a00a76a.akpm@linux-foundation.org> <4F4C983002000078000751AE@nat28.tlf.novell.com> <20120228001210.26b59479.akpm@linux-foundation.org> In-Reply-To: <20120228001210.26b59479.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 28.02.12 at 09:12, Andrew Morton wrote: > On Tue, 28 Feb 2012 08:02:40 +0000 "Jan Beulich" wrote: > >> >>> On 28.02.12 at 08:44, Andrew Morton wrote: >> > 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? >> >> Sorry, Andrew, but this makes no sense to me. > > I really don't care - anywhere you like. Just the darn changelog, if > nowhere else. > > I still don't have an answer to my question :( Some statement > describing what the new section is *for*. Seems a pretty important > thing? Oh, sorry - to carry static data the accesses to which are unlikely (i.e., as in the case given, fully contained in code sections inside conditionals which themselves use unlikely() on their primary/only clause - in other words, something that the compiler really could do on its own). Jan