Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757980AbYKDQ4x (ORCPT ); Tue, 4 Nov 2008 11:56:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758146AbYKDQ4c (ORCPT ); Tue, 4 Nov 2008 11:56:32 -0500 Received: from one.firstfloor.org ([213.235.205.2]:52158 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758123AbYKDQ4b (ORCPT ); Tue, 4 Nov 2008 11:56:31 -0500 Date: Tue, 4 Nov 2008 18:05:01 +0100 From: Andi Kleen To: Cyrill Gorcunov Cc: Alexander van Heukelum , LKML , Ingo Molnar , heukelum@fastmail.fm, Thomas Gleixner , "H. Peter Anvin" , lguest@ozlabs.org, jeremy@xensource.com, Steven Rostedt , Mike Travis , Andi Kleen Subject: Re: [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes Message-ID: <20081104170501.GE29626@one.firstfloor.org> References: <20081104122839.GA22864@mailshack.com> <20081104150729.GC21470@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081104150729.GC21470@localhost> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1170 Lines: 30 > not taking into account the cost of cs reading (which I > don't suspect to be that expensive apart from writting, GDT accesses have an implied LOCK prefix. Especially on some older CPUs that could be slow. I don't know if it's a problem or not but it would need some careful benchmarking on different systems to make sure interrupt latencies are not impacted. Another reason I would be also careful with this patch is that it will likely trigger slow paths in JITs like qemu/vmware/etc. Also code segment switching is likely not something that current and future micro architectures will spend a lot of time optimizing. I'm not sure that risk is worth the small improvement in code size. An alternative BTW to having all the stubs in the executable would be to just dynamically generate them when the interrupt is set up. Then you would only have the stubs around for the interrupts which are actually used. -Andi -- 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/