From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH] reduce export symbol CRC table size on 64-bit archs Date: Wed, 1 Jul 2009 00:09:32 +0200 Message-ID: <20090630220932.GE1241@elte.hu> References: <4A4A18780200007800008345@vpn.id2.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:46439 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753612AbZF3WJo (ORCPT ); Tue, 30 Jun 2009 18:09:44 -0400 Content-Disposition: inline In-Reply-To: <4A4A18780200007800008345@vpn.id2.novell.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Jan Beulich Cc: tony.luck@intel.com, Thomas Gleixner , Rusty Russell , hpa@zytor.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org * Jan Beulich wrote: > Since these CRCs are really only 32-bit quantities, there's no > need to store them in 64-bit slots. Since, however, gcc doesn't > allow respective initializations, asm() constructs get used to > create the CRC tables (and its for that reason that the patch only > makes x86-64 and ia64 utilize that functionality, as I can't > verify this doesn't break in some subtle way elsewhere). > > Observed size reduction (x86-64): > - 16k kernel resident size > - 2k module resident size > - 1M vmlinux image size > > If the asm() construct could be extended to all architectures, and > if modpost would guarantee generation of CRCs for all exported, > then the __crc_* symbols wouldn't need to be declared weak > anymore, could hence remain local to the exporting object. By > adding -Wa,-strip-local-absolute to the second compilation step > the __crc_* symbols could even be prevented from making it into > any object file at all. > > Signed-off-by: Jan Beulich > > --- > arch/ia64/include/asm/module.h | 2 ++ > arch/x86/include/asm/module.h | 1 + > include/linux/module.h | 41 ++++++++++++++++++++++++++--------------- > include/linux/moduleparam.h | 10 +++++++++- > kernel/module.c | 26 +++++++++++++------------- > scripts/genksyms/genksyms.c | 16 ++++++++-------- > 6 files changed, 59 insertions(+), 37 deletions(-) No objections to the (minor) x86 bits. Ingo