From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751947AbcEYVCW (ORCPT ); Wed, 25 May 2016 17:02:22 -0400 Received: from mout.kundenserver.de ([212.227.126.134]:59486 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750867AbcEYVCU (ORCPT ); Wed, 25 May 2016 17:02:20 -0400 From: Arnd Bergmann To: David Miller Cc: ynorov@caviumnetworks.com, catalin.marinas@arm.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 Date: Wed, 25 May 2016 23:01:06 +0200 Message-ID: <6407614.fdv5XFSBue@wuerfel> User-Agent: KMail/5.1.3 (Linux/4.4.0-22-generic; KDE/5.18.0; x86_64; ; ) In-Reply-To: <20160525.135039.244098606649448826.davem@davemloft.net> References: <20160525200327.GA22395@yury-N73SV> <6293194.tGy03QJ9ME@wuerfel> <20160525.135039.244098606649448826.davem@davemloft.net> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:1N2gugAIQF2qXUoADEXczabllv8MN+dYL7KgnVUjbLlQBeDZd1o tXJ1NDqzfwDrP/TYxrSvZOXIXxAVQqv5iDjxs6AaDPrCNQ8xS6Iv4uKaCNCzV5Nw0/AWxa2 60rCM/b64wO14fCofxYilviLxnMmGYaQa2fJdV9UBG1myR//kRiyTPyvSIJsUoygEdwhVpv sAd8fmnP4y5+sIUk3ZUhg== X-UI-Out-Filterresults: notjunk:1;V01:K0:P6pzbXNzokA=:ciSDk4DhGW1o6s+lg+r6KI ceu/zwUpj0VdnatUqDyBeTuC3IIpJ+eZrwVfDuNZvBFtgXiSXjgsGTn1RlaJwX8LQTKbZVh43 aJvqrQrhNk66g34olAcXEyPqAbAbo3rSGI3080Hui25d957t7I86yqySQQSBESBPeuYKA82D1 RJwLjkFiWtacDFQ9t8nZZ3dwRLN0OoOANGZRo6BLeTBFqJLsCMdikW2aWXR24eFiFDYvanWeL I3lxlt8ZkjyWTB0pw9vQhVG/+v6WzVjgz3qwDnyZhpjUnB7DMTmy1GDB2XAMinqOtnXN1IP4t vCSuE6J8d0Igq1wwoXQgmqt+DfQXoBhX9UMu7q3/u/Wr9hrtfASOXd/rL95h2pd1ugxSXC2S+ KulG9lmB7fvNXJG5O3lYCq9QLad1MISuRoNJ2onoH9IvOkRVZpJZojFjWTWO2o+KAeV890wKf tt7TTyH2bx8CSkrP0wn4ALuRAXJk6uCI/Wyr+UHo0ESI+SF+R6l8f2BF1oItIudiX/LeVnbzZ 4M2NFg9Mqa7e2pmrIar81KzlTE+zc4iOvUe9gHsEXfk2c2RS7SjFV2s0PinfEIdoEAXjg9dfi ORe8s8bA4zCJ1ByVxYAen7RpP++QuKSjameS3QeARw0RFqW/6tldB1H1T79SuM85RSQ6+r+7y V5joLcHplM0m4rtARLDg8WdlvVN3Z72j+2dpGrZUrfsUHQxNdQgcD4jpq2U5riEiSWjLHLQFQ O2xzyITyP6+rn/zv Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, May 25, 2016 1:50:39 PM CEST David Miller wrote: > From: Arnd Bergmann > Date: Wed, 25 May 2016 22:47:33 +0200 > > > If we use the normal calling conventions, we could remove these overrides > > along with the respective special-case handling in glibc. None of them > > look particularly performance-sensitive, but I could be wrong there. > > You could set the lowest bit in the system call entry pointer to indicate > the upper-half clears should be elided. Right, but that would introduce an extra conditional branch in the syscall hotpath, and likely eliminate the gains from passing the loff_t arguments in a single register instead of a pair. Arnd