From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753754AbeCPKie (ORCPT ); Fri, 16 Mar 2018 06:38:34 -0400 Received: from isilmar-4.linta.de ([136.243.71.142]:49092 "EHLO isilmar-4.linta.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753735AbeCPKic (ORCPT ); Fri, 16 Mar 2018 06:38:32 -0400 Date: Fri, 16 Mar 2018 11:25:06 +0100 From: Dominik Brodowski To: "Zhang, Ning A" Cc: "torvalds@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "viro@zeniv.linux.org.uk" , "mingo@kernel.org" , "luto@kernel.org" , "akpm@linux-foundation.org" , "arnd@arndb.de" Subject: Re: [PATCH v2 00/36] remove in-kernel syscall invocations (part 1) Message-ID: <20180316102506.GA769@light.dominikbrodowski.net> References: <20180315190529.20943-1-linux@dominikbrodowski.net> <1521190870.1367.33.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1521190870.1367.33.camel@intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 16, 2018 at 09:01:11AM +0000, Zhang, Ning A wrote: > 在 2018-03-15四的 20:04 +0100，Dominik Brodowski写道： > > Here is a re-spin of the first set of patches which reduce the number of > > syscall invocations from within the kernel; the RFC may be found at > > > > The rationale for this change is described in patch 1 as follows: > > > > The syscall entry points to the kernel defined by SYSCALL_DEFINEx() > > and COMPAT_SYSCALL_DEFINEx() should only be called from userspace > > through kernel entry points, but not from the kernel itself. This > > will allow cleanups and optimizations to the entry paths *and* to > > the parts of the kernel code which currently need to pretend to be > > userspace in order to make use of syscalls. > > I think this is really bad to change syscalls one by one, to do_* > > why not change SYSCALL_DEFINEx to define kernel wrappers? Basically, for two reasons: First, only a subset of all syscalls require such wrappers -- only about a third of all syscalls are called from within the kernel at the moment (rough guess). Second, and more important: We want to reduce the amount of such usage; see, e.g., the messages by Christoph and Arnd in this thread. Thanks, Dominik