Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758630AbZFIRzm (ORCPT ); Tue, 9 Jun 2009 13:55:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754907AbZFIRzg (ORCPT ); Tue, 9 Jun 2009 13:55:36 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60047 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754535AbZFIRzf (ORCPT ); Tue, 9 Jun 2009 13:55:35 -0400 Message-ID: <4A2E82BA.7040905@zytor.com> Date: Tue, 09 Jun 2009 08:41:46 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Roland McGrath CC: Petr Tesarik , Sam Ravnborg , LKML , Thomas Gleixner , Ingo Molnar , Andi Kleen Subject: Re: [PATCH] x86: clean up vdso-layout.lds.S References: <1243865115.24278.8.camel@nathan.suse.cz> <1244215559.1604.12.camel@nathan.suse.cz> <20090605200701.GB23195@uranus.ravnborg.org> <1244532418.5199.24.camel@nathan.suse.cz> <20090609075247.DA95CFC3B2@magilla.sf.frob.com> In-Reply-To: <20090609075247.DA95CFC3B2@magilla.sf.frob.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1118 Lines: 35 Roland McGrath wrote: > > You mean this one: > > /* > * Align the actual code well away from the non-instruction data. > * This is the best thing for the I-cache. > */ > . = ALIGN(0x100); > > Reading the comment might make it obvious that it's intended for optimal > code alignment. I suspect someone at the time told me 256 is as big as an > I-cache line was ever likely to get. You could use L1_CACHE_BYTES instead > I suppose. > Most likely 256 was chosen as a compromise between the the then-documented value for coherency avoidance (128), future-proofing, and waste. I don't think we want to use different values on different platforms, and end up with dramatically different vdsos when they still need to fit in the same size envelope. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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/