Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754874Ab0AEP1U (ORCPT ); Tue, 5 Jan 2010 10:27:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753568Ab0AEP1T (ORCPT ); Tue, 5 Jan 2010 10:27:19 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:47975 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752862Ab0AEP1S (ORCPT ); Tue, 5 Jan 2010 10:27:18 -0500 Date: Tue, 5 Jan 2010 07:26:31 -0800 (PST) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: KAMEZAWA Hiroyuki cc: Minchan Kim , Peter Zijlstra , "Paul E. McKenney" , Peter Zijlstra , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , cl@linux-foundation.org, "hugh.dickins" , Nick Piggin , Ingo Molnar Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault() In-Reply-To: <20100105163939.a3f146fb.kamezawa.hiroyu@jp.fujitsu.com> Message-ID: References: <20100104182429.833180340@chello.nl> <20100104182813.753545361@chello.nl> <20100105092559.1de8b613.kamezawa.hiroyu@jp.fujitsu.com> <28c262361001042029w4b95f226lf54a3ed6a4291a3b@mail.gmail.com> <20100105134357.4bfb4951.kamezawa.hiroyu@jp.fujitsu.com> <20100105143046.73938ea2.kamezawa.hiroyu@jp.fujitsu.com> <20100105163939.a3f146fb.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1540 Lines: 47 On Tue, 5 Jan 2010, KAMEZAWA Hiroyuki wrote: > # > # Overhead Command Shared Object Symbol > # ........ ............... ........................ ...... > # > 43.23% multi-fault-all [kernel] [k] smp_invalidate_interrupt > 16.27% multi-fault-all [kernel] [k] flush_tlb_others_ipi > 11.55% multi-fault-all [kernel] [k] _raw_spin_lock_irqsave <========(*) > 6.23% multi-fault-all [kernel] [k] intel_pmu_enable_all > 2.17% multi-fault-all [kernel] [k] _raw_spin_unlock_irqrestore Hmm.. The default rwsem implementation shouldn't have any spin-locks in the fast-path. And your profile doesn't seem to have any scheduler footprint, so I wonder what is going on. Oh. Lookie here: - arch/x86/Kconfig.cpu: config X86_XADD def_bool y depends on X86_32 && !M386 - arch/x86/Kconfig: config RWSEM_GENERIC_SPINLOCK def_bool !X86_XADD config RWSEM_XCHGADD_ALGORITHM def_bool X86_XADD it looks like X86_XADD only gets enabled on 32-bit builds. Which means that x86-64 in turn seems to end up always using the slower "generic spinlock" version. Are you sure this isn't the reason why your profiles are horrible? Linus -- 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/