Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751875AbZDJENr (ORCPT ); Fri, 10 Apr 2009 00:13:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750745AbZDJENi (ORCPT ); Fri, 10 Apr 2009 00:13:38 -0400 Received: from hera.kernel.org ([140.211.167.34]:49379 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750730AbZDJENh (ORCPT ); Fri, 10 Apr 2009 00:13:37 -0400 Subject: Re: [PATCH 09/30] x86_64: ifdef out struct thread_struct::ip From: Jaswinder Singh Rajput To: Matt Helsley Cc: Alexey Dobriyan , akpm@linux-foundation.org, containers@lists.linux-foundation.org, xemul@parallels.com, linux-kernel@vger.kernel.org, dave@linux.vnet.ibm.com, hch@infradead.org, mingo@elte.hu, torvalds@linux-foundation.org In-Reply-To: <20090410035328.GB29496@us.ibm.com> References: <20090410023522.GJ27788@x200.localdomain> <20090410035328.GB29496@us.ibm.com> Content-Type: text/plain Date: Fri, 10 Apr 2009 09:40:39 +0530 Message-Id: <1239336639.3036.20.camel@ht.satnam> Mime-Version: 1.0 X-Mailer: Evolution 2.24.5 (2.24.5-1.fc10) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1817 Lines: 59 On Thu, 2009-04-09 at 20:53 -0700, Matt Helsley wrote: > On Fri, Apr 10, 2009 at 06:35:22AM +0400, Alexey Dobriyan wrote: > > struct thread_struct::ip isn't used on x86_64, struct pt_regs::ip is used > > instead. > > > > kgdb should be reading 0, but I can't check it. > > > > Signed-off-by: Alexey Dobriyan > > --- > > > > arch/x86/include/asm/processor.h | 2 ++ > > arch/x86/kernel/kgdb.c | 2 +- > > 2 files changed, 3 insertions(+), 1 deletion(-) > > > > --- a/arch/x86/include/asm/processor.h > > +++ b/arch/x86/include/asm/processor.h > > @@ -421,7 +421,9 @@ struct thread_struct { > > unsigned short fsindex; > > unsigned short gsindex; > > #endif > > +#ifdef CONFIG_X86_32 > > unsigned long ip; > > +#endif > > #ifdef CONFIG_X86_64 > > unsigned long fs; > > #endif > > Do these make struct thread_struct behave better in cachelines (smaller, > less aliasing)? Can we really fit more in the slab du jour? > > Otherwise it seems like we're littering these structs with #ifdefs > and not really saving anything. If these #ifdefs don't save any space why not > just put in a comment: > > > unsigned long ip; /* Used only on i386 */ > > Or maybe even: > > union { > unsigned long ip; /* Used only on i386 */ > unsigned long fs; /* Used only on x86_64 */ > }; > Can we do it like this: unsigned long ip_fs; /* ip: i386, fs: x86_64 */ I am using same variable for both cases, or we can use some better name than ip_fs. I am assuming either it is i386 or x86_64 machine ;-) -- JSR -- 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/