Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755223Ab0AFAZf (ORCPT ); Tue, 5 Jan 2010 19:25:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754681Ab0AFAZe (ORCPT ); Tue, 5 Jan 2010 19:25:34 -0500 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:47046 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754508Ab0AFAZd (ORCPT ); Tue, 5 Jan 2010 19:25:33 -0500 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Wed, 6 Jan 2010 09:22:12 +0900 From: KAMEZAWA Hiroyuki To: Linus Torvalds 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() Message-Id: <20100106092212.c8766aa8.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: 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> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.7.1 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2850 Lines: 89 On Tue, 5 Jan 2010 07:26:31 -0800 (PST) Linus Torvalds wrote: > > > 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? > I think this is the 1st reason but haven't rewrote rwsem itself and tested, sorry. This is a profile in other test. == 2.6.33-rc2's score of the same test program is here. 75.42% multi-fault-all [kernel] [k] _raw_spin_lock_irqsav | --- _raw_spin_lock_irqsave | |--49.13%-- __down_read_trylock | down_read_trylock | do_page_fault | page_fault | 0x400950 | | | --100.00%-- (nil) | |--46.92%-- __up_read | up_read | | | |--99.99%-- do_page_fault | | page_fault | | 0x400950 | | (nil) | --0.01%-- [...] == yes, spinlock is from rwsem. Why I tried "skipping rwsem" is because I like avoid locking rather than rewrite lock itself when I think of the influence of the patch.... Thanks, -Kame -- 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/