From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932107AbcEZTnt (ORCPT ); Thu, 26 May 2016 15:43:49 -0400 Received: from shards.monkeyblade.net ([149.20.54.216]:53868 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754727AbcEZTnr (ORCPT ); Thu, 26 May 2016 15:43:47 -0400 Date: Thu, 26 May 2016 12:43:44 -0700 (PDT) Message-Id: <20160526.124344.1660236473079504674.davem@davemloft.net> To: catalin.marinas@arm.com Cc: arnd@arndb.de, ynorov@caviumnetworks.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, libc-alpha@sourceware.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, pinskia@gmail.com, broonie@kernel.org, joseph@codesourcery.com, christoph.muellner@theobroma-systems.com, bamvor.zhangjian@huawei.com, szabolcs.nagy@arm.com, klimov.linux@gmail.com, Nathan_Lynch@mentor.com, agraf@suse.de, Prasun.Kapoor@caviumnetworks.com, kilobyte@angband.pl, geert@linux-m68k.org, philipp.tomsich@theobroma-systems.com Subject: Re: [PATCH 01/23] all: syscall wrappers: add documentation From: David Miller In-Reply-To: <20160526142057.GA7456@e104818-lin.cambridge.arm.com> References: <6407614.fdv5XFSBue@wuerfel> <20160525.142821.1719403997976778673.davem@davemloft.net> <20160526142057.GA7456@e104818-lin.cambridge.arm.com> X-Mailer: Mew version 6.7 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Thu, 26 May 2016 12:43:46 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Catalin Marinas Date: Thu, 26 May 2016 15:20:58 +0100 > We can solve (a) by adding more __SC_WRAP annotations in the generic > unistd.h. ... I really think it's much more robust to clear the tops of the registers by default. Then you won't be auditing constantly and adding more and more wrappers. You can't even quantify the performance gains for me in any precise way. Whatever you gain by avoiding the 64-bit decompostion/reconstitution for those few system calls with 64-bit registers, you are losing by calling the wrappers for more common system calls, more often. "it's more natural to pass 64-bit values in a register" is not a clear justification for this change. This looks way over engineered to me. From mboxrd@z Thu Jan 1 00:00:00 1970 From: davem@davemloft.net (David Miller) Date: Thu, 26 May 2016 12:43:44 -0700 (PDT) Subject: [PATCH 01/23] all: syscall wrappers: add documentation In-Reply-To: <20160526142057.GA7456@e104818-lin.cambridge.arm.com> References: <6407614.fdv5XFSBue@wuerfel> <20160525.142821.1719403997976778673.davem@davemloft.net> <20160526142057.GA7456@e104818-lin.cambridge.arm.com> Message-ID: <20160526.124344.1660236473079504674.davem@davemloft.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Catalin Marinas Date: Thu, 26 May 2016 15:20:58 +0100 > We can solve (a) by adding more __SC_WRAP annotations in the generic > unistd.h. ... I really think it's much more robust to clear the tops of the registers by default. Then you won't be auditing constantly and adding more and more wrappers. You can't even quantify the performance gains for me in any precise way. Whatever you gain by avoiding the 64-bit decompostion/reconstitution for those few system calls with 64-bit registers, you are losing by calling the wrappers for more common system calls, more often. "it's more natural to pass 64-bit values in a register" is not a clear justification for this change. This looks way over engineered to me.