From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id A9D906007E1 for ; Tue, 5 Jan 2010 10:27:14 -0500 (EST) Date: Tue, 5 Jan 2010 07:26:31 -0800 (PST) From: Linus Torvalds 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org 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 List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org