From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F815C10F0B for ; Wed, 20 Feb 2019 14:47:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F093F21848 for ; Wed, 20 Feb 2019 14:47:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727266AbfBTOr0 (ORCPT ); Wed, 20 Feb 2019 09:47:26 -0500 Received: from foss.arm.com ([217.140.101.70]:59164 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726592AbfBTOrZ (ORCPT ); Wed, 20 Feb 2019 09:47:25 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2B34615AB; Wed, 20 Feb 2019 06:47:25 -0800 (PST) Received: from fuggles.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2EF1B3F5C1; Wed, 20 Feb 2019 06:47:20 -0800 (PST) Date: Wed, 20 Feb 2019 14:47:17 +0000 From: Will Deacon To: Waiman Long Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-c6x-dev@linux-c6x.org, uclinux-h8-devel@lists.sourceforge.jp, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, nios2-dev@lists.rocketboards.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org, x86@kernel.org, Arnd Bergmann , Borislav Petkov , "H. Peter Anvin" , Davidlohr Bueso , Linus Torvalds , Andrew Morton , Tim Chen Subject: Re: [PATCH v4 1/3] locking/rwsem: Remove arch specific rwsem files Message-ID: <20190220144717.GI7523@fuggles.cambridge.arm.com> References: <1550095217-12047-1-git-send-email-longman@redhat.com> <1550095217-12047-2-git-send-email-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1550095217-12047-2-git-send-email-longman@redhat.com> User-Agent: Mutt/1.11.1+86 (6f28e57d73f2) () Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Wed, Feb 13, 2019 at 05:00:15PM -0500, Waiman Long wrote: > As the generic rwsem-xadd code is using the appropriate acquire and > release versions of the atomic operations, the arch specific rwsem.h > files will not be that much faster than the generic code as long as the > atomic functions are properly implemented. So we can remove those arch > specific rwsem.h and stop building asm/rwsem.h to reduce maintenance > effort. > > Currently, only x86, alpha and ia64 have implemented architecture > specific fast paths. I don't have access to alpha and ia64 systems for > testing, but they are legacy systems that are not likely to be updated > to the latest kernel anyway. > > By using a rwsem microbenchmark, the total locking rates on a 4-socket > 56-core 112-thread x86-64 system before and after the patch were as > follows (mixed means equal # of read and write locks): > > Before Patch After Patch > # of Threads wlock rlock mixed wlock rlock mixed > ------------ ----- ----- ----- ----- ----- ----- > 1 29,201 30,143 29,458 28,615 30,172 29,201 > 2 6,807 13,299 1,171 7,725 15,025 1,804 > 4 6,504 12,755 1,520 7,127 14,286 1,345 > 8 6,762 13,412 764 6,826 13,652 726 > 16 6,693 15,408 662 6,599 15,938 626 > 32 6,145 15,286 496 5,549 15,487 511 > 64 5,812 15,495 60 5,858 15,572 60 > > There were some run-to-run variations for the multi-thread tests. For > x86-64, using the generic C code fast path seems to be a little bit > faster than the assembly version with low lock contention. Looking at > the assembly version of the fast paths, there are assembly to/from C > code wrappers that save and restore all the callee-clobbered registers > (7 registers on x86-64). The assembly generated from the generic C > code doesn't need to do that. That may explain the slight performance > gain here. > > The generic asm rwsem.h can also be merged into kernel/locking/rwsem.h > with no code change as no other code other than those under > kernel/locking needs to access the internal rwsem macros and functions. > > Signed-off-by: Waiman Long > --- > MAINTAINERS | 1 - > arch/alpha/include/asm/rwsem.h | 211 ----------------------------------- > arch/arm/include/asm/Kbuild | 1 - > arch/arm64/include/asm/Kbuild | 1 - > arch/hexagon/include/asm/Kbuild | 1 - > arch/ia64/include/asm/rwsem.h | 172 ----------------------------- > arch/powerpc/include/asm/Kbuild | 1 - > arch/s390/include/asm/Kbuild | 1 - > arch/sh/include/asm/Kbuild | 1 - > arch/sparc/include/asm/Kbuild | 1 - > arch/x86/include/asm/rwsem.h | 237 ---------------------------------------- > arch/x86/lib/Makefile | 1 - > arch/x86/lib/rwsem.S | 156 -------------------------- > arch/x86/um/Makefile | 1 - > arch/xtensa/include/asm/Kbuild | 1 - > include/asm-generic/rwsem.h | 140 ------------------------ > include/linux/rwsem.h | 4 +- > kernel/locking/percpu-rwsem.c | 2 + > kernel/locking/rwsem.h | 130 ++++++++++++++++++++++ > 19 files changed, 133 insertions(+), 930 deletions(-) > delete mode 100644 arch/alpha/include/asm/rwsem.h > delete mode 100644 arch/ia64/include/asm/rwsem.h > delete mode 100644 arch/x86/include/asm/rwsem.h > delete mode 100644 arch/x86/lib/rwsem.S > delete mode 100644 include/asm-generic/rwsem.h Looks like a nice cleanup, thanks: Acked-by: Will Deacon Will