From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [RFC 1/4] asm-generic/uaccess: don't define inline functions if noinline lib/* in use Date: Wed, 15 Jan 2020 14:12:24 +0000 Message-ID: <20200115141224.GH8904@ZenIV.linux.org.uk> References: <20200114200846.29434-1-vgupta@synopsys.com> <20200114200846.29434-2-vgupta@synopsys.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Arnd Bergmann Cc: Linus Torvalds , Vineet Gupta , Khalid Aziz , Andrey Konovalov , Andrew Morton , Peter Zijlstra , Christian Brauner , Kees Cook , Ingo Molnar , Aleksa Sarai , "open list:SYNOPSYS ARC ARCHITECTURE" , Linux Kernel Mailing List , linux-arch List-Id: linux-arch.vger.kernel.org On Wed, Jan 15, 2020 at 10:08:31AM +0100, Arnd Bergmann wrote: > > I would suggest that anybody who uses asm-generic/uaccess.h needs to > > simply use the generic library version. > > Or possibly just everybody altogether: the remaining architectures that > have a custom implementation don't seem to be doing any better either. No go for s390. There you really want to access userland memory in larger chunks - it's oriented for block transfers. IIRC, the insn they are using has a costly setup phase, independent of the amount to copy, followed by reasonably fast transfer more or less linear by the size. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zeniv.linux.org.uk ([195.92.253.2]:57496 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726440AbgAOOMz (ORCPT ); Wed, 15 Jan 2020 09:12:55 -0500 Date: Wed, 15 Jan 2020 14:12:24 +0000 From: Al Viro Subject: Re: [RFC 1/4] asm-generic/uaccess: don't define inline functions if noinline lib/* in use Message-ID: <20200115141224.GH8904@ZenIV.linux.org.uk> References: <20200114200846.29434-1-vgupta@synopsys.com> <20200114200846.29434-2-vgupta@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Arnd Bergmann Cc: Linus Torvalds , Vineet Gupta , Khalid Aziz , Andrey Konovalov , Andrew Morton , Peter Zijlstra , Christian Brauner , Kees Cook , Ingo Molnar , Aleksa Sarai , "open list:SYNOPSYS ARC ARCHITECTURE" , Linux Kernel Mailing List , linux-arch Message-ID: <20200115141224.sUEeC3CPSIbLAiGIejckf77u5dJlY9yrRoEv6g11p-g@z> On Wed, Jan 15, 2020 at 10:08:31AM +0100, Arnd Bergmann wrote: > > I would suggest that anybody who uses asm-generic/uaccess.h needs to > > simply use the generic library version. > > Or possibly just everybody altogether: the remaining architectures that > have a custom implementation don't seem to be doing any better either. No go for s390. There you really want to access userland memory in larger chunks - it's oriented for block transfers. IIRC, the insn they are using has a costly setup phase, independent of the amount to copy, followed by reasonably fast transfer more or less linear by the size.