From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Subject: Re: [RFC 10/12] x86, rwsem: simplify __down_write Date: Thu, 09 Jun 2016 15:40:58 +0100 Message-ID: <29355.1465483258@warthog.procyon.org.uk> References: <20160603223417.GB3892@twins.programming.kicks-ass.net> <1454444369-2146-1-git-send-email-mhocko@kernel.org> <1454444369-2146-11-git-send-email-mhocko@kernel.org> <20160203081016.GD32652@gmail.com> <20160603161339.GC3693@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: In-Reply-To: <20160603223417.GB3892@twins.programming.kicks-ass.net> Content-ID: <29354.1465483258.1@warthog.procyon.org.uk> Sender: linux-ia64-owner@vger.kernel.org To: Peter Zijlstra Cc: dhowells@redhat.com, Ingo Molnar , Michal Hocko , LKML , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , "David S. Miller" , Tony Luck , Andrew Morton , Chris Zankel , Max Filippov , x86@kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org, Michal Hocko , Linus Torvalds , "Paul E. McKenney" , Jason Low List-Id: linux-arch.vger.kernel.org Peter Zijlstra wrote: > Blergh; so looking at more asm there's still a few tricks we cannot do. > So while overall size is down, some paths do end up more expensive. (It > typically boils down to creative use of condition flags, which is very > hard in C) It can be done using ISO __atomic_fetch_add() and suchlike. David From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:48646 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932069AbcFIOlE (ORCPT ); Thu, 9 Jun 2016 10:41:04 -0400 From: David Howells In-Reply-To: <20160603223417.GB3892@twins.programming.kicks-ass.net> References: <20160603223417.GB3892@twins.programming.kicks-ass.net> <1454444369-2146-1-git-send-email-mhocko@kernel.org> <1454444369-2146-11-git-send-email-mhocko@kernel.org> <20160203081016.GD32652@gmail.com> <20160603161339.GC3693@twins.programming.kicks-ass.net> Subject: Re: [RFC 10/12] x86, rwsem: simplify __down_write MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <29354.1465483258.1@warthog.procyon.org.uk> Date: Thu, 09 Jun 2016 15:40:58 +0100 Message-ID: <29355.1465483258@warthog.procyon.org.uk> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: dhowells@redhat.com, Ingo Molnar , Michal Hocko , LKML , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , "David S. Miller" , Tony Luck , Andrew Morton , Chris Zankel , Max Filippov , x86@kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org, Michal Hocko , Linus Torvalds , "Paul E. McKenney" , Jason Low Message-ID: <20160609144058.WuqTGWMTOv2G4chNwGrn42i2iiNPeb2SlLgraMB73fw@z> Peter Zijlstra wrote: > Blergh; so looking at more asm there's still a few tricks we cannot do. > So while overall size is down, some paths do end up more expensive. (It > typically boils down to creative use of condition flags, which is very > hard in C) It can be done using ISO __atomic_fetch_add() and suchlike. David