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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 AA709C18E5B for ; Sun, 15 Mar 2020 18:32:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 802CE206BE for ; Sun, 15 Mar 2020 18:32:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728536AbgCOScb (ORCPT ); Sun, 15 Mar 2020 14:32:31 -0400 Received: from foss.arm.com ([217.140.110.172]:34626 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727399AbgCOScb (ORCPT ); Sun, 15 Mar 2020 14:32:31 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E967D1FB; Sun, 15 Mar 2020 11:32:29 -0700 (PDT) Received: from mbp (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BEC763F67D; Sun, 15 Mar 2020 11:32:26 -0700 (PDT) Date: Sun, 15 Mar 2020 18:32:16 +0000 From: Catalin Marinas To: Vincenzo Frascino Cc: linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, clang-built-linux@googlegroups.com, x86@kernel.org, Will Deacon , Arnd Bergmann , Russell King , Paul Burton , Thomas Gleixner , Andy Lutomirski , Ingo Molnar , Borislav Petkov , Stephen Boyd , Mark Salyzyn , Kees Cook , Peter Collingbourne , Dmitry Safonov <0x7f454c46@gmail.com>, Andrei Vagin , Nick Desaulniers , Marc Zyngier , Mark Rutland , Will Deacon Subject: Re: [PATCH v3 21/26] arm64: Introduce asm/vdso/arch_timer.h Message-ID: <20200315183151.GE32205@mbp> References: <20200313154345.56760-1-vincenzo.frascino@arm.com> <20200313154345.56760-22-vincenzo.frascino@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200313154345.56760-22-vincenzo.frascino@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 13, 2020 at 03:43:40PM +0000, Vincenzo Frascino wrote: > The vDSO library should only include the necessary headers required for > a userspace library (UAPI and a minimal set of kernel headers). To make > this possible it is necessary to isolate from the kernel headers the > common parts that are strictly necessary to build the library. > > Introduce asm/vdso/arch_timer.h to contain all the arm64 specific > code. This allows to replace the second isb() in __arch_get_hw_counter() > with a fake dependent stack read of the counter which improves the vdso > library peformances of ~4.5%. Below the results of vdsotest [1] ran for > 100 iterations. The subject seems to imply a non-functional change but as you read, it gets a lot more complicated. Could you keep the functional change separate from the header clean-up, maybe submit it as an independent patch? And it shouldn't go in without Will's ack ;). -- Catalin