Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267799AbUIPG44 (ORCPT ); Thu, 16 Sep 2004 02:56:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267772AbUIPG4z (ORCPT ); Thu, 16 Sep 2004 02:56:55 -0400 Received: from mx1.elte.hu ([157.181.1.137]:9184 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S267777AbUIPG4q (ORCPT ); Thu, 16 Sep 2004 02:56:46 -0400 Date: Thu, 16 Sep 2004 08:58:05 +0200 From: Ingo Molnar To: Andi Kleen Cc: Andrew Morton , Zwane Mwaikambo , linux-kernel@vger.kernel.org, wli@holomorphy.com Subject: Re: [PATCH] remove LOCK_SECTION from x86_64 spin_lock asm Message-ID: <20040916065805.GA12244@elte.hu> References: <20040915144523.0fec2070.akpm@osdl.org> <20040916061359.GA12915@wotan.suse.de> <20040916062759.GA10527@elte.hu> <20040916064428.GD12915@wotan.suse.de> <20040916065101.GA11726@elte.hu> <20040916065342.GE12915@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040916065342.GE12915@wotan.suse.de> User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1010 Lines: 24 * Andi Kleen wrote: > > the alternative would be to unwind the stack - quite some task on some > > platforms ... > > Sometimes call graph profiling would be very useful, but I wouldn't > want the profiler to do it by default, especially not for this silly > simple case. dwarf2 unwinding is complex enough that just requiring > frame pointers for the CG case would look attractive. but ... frame pointers are overhead to all of the kernel. (the overhead is less pronounced on architectures with more registers, but even with 15 registers, 14 or 15 can still be a difference.) While unwinding is overhead to profiling only - if enabled. Also, there could be other functionality (exception handling?) that could benefit from dwarf2 unwinding. Ingo - 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/