From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH 1/11] Add generic helpers for arch IPI function calls Date: Mon, 28 Apr 2008 10:43:32 -0400 Message-ID: <1209393812.3367.24.camel@localhost.localdomain> References: <1209219236.3113.6.camel@localhost.localdomain> <1208890227-24808-1-git-send-email-jens.axboe@oracle.com> <1208890227-24808-2-git-send-email-jens.axboe@oracle.com> <20080425231100.b93a1601.akpm@linux-foundation.org> <18470.1209392727@redhat.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <18470.1209392727-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-arch-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: To: David Howells Cc: Andrew Morton , Jens Axboe , linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, npiggin-l3A5Bk7waGM@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, sam-uyr5N9Q2VtJg9hUCZPvPmw@public.gmane.org, "Paul E. McKenney" On Mon, 2008-04-28 at 15:25 +0100, David Howells wrote: > We could use a GOT, but I believe that would add an extra memory > access to any > memory access or jump - which I'd prefer to avoid. Not necessarily; this is how we work on PARISC with a GOT as the ELF spec defines. The point is that the GOT is linker constructed, so we only lay down GOT entries when the linker sees that relative displacements fail, so they don't consume memory (or even get brought into existence) in the ordinary case. The flip side of this is that we do double jump (relative to jump through got) for the long displacements we can't reach. James From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from accolon.hansenpartnership.com ([76.243.235.52]:41042 "EHLO accolon.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932106AbYD1Onk (ORCPT ); Mon, 28 Apr 2008 10:43:40 -0400 Subject: Re: [PATCH 1/11] Add generic helpers for arch IPI function calls From: James Bottomley In-Reply-To: <18470.1209392727@redhat.com> References: <1209219236.3113.6.camel@localhost.localdomain> <1208890227-24808-1-git-send-email-jens.axboe@oracle.com> <1208890227-24808-2-git-send-email-jens.axboe@oracle.com> <20080425231100.b93a1601.akpm@linux-foundation.org> <18470.1209392727@redhat.com> Content-Type: text/plain Date: Mon, 28 Apr 2008 10:43:32 -0400 Message-ID: <1209393812.3367.24.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Howells Cc: Andrew Morton , Jens Axboe , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, npiggin@suse.de, torvalds@linux-foundation.org, peterz@infradead.org, sam@ravnborg.org, "Paul E. McKenney" Message-ID: <20080428144332.wDnFRGeUBZjTsaVzyY8bIB9n3CqKdPcrhLK8dfYFAx0@z> On Mon, 2008-04-28 at 15:25 +0100, David Howells wrote: > We could use a GOT, but I believe that would add an extra memory > access to any > memory access or jump - which I'd prefer to avoid. Not necessarily; this is how we work on PARISC with a GOT as the ELF spec defines. The point is that the GOT is linker constructed, so we only lay down GOT entries when the linker sees that relative displacements fail, so they don't consume memory (or even get brought into existence) in the ordinary case. The flip side of this is that we do double jump (relative to jump through got) for the long displacements we can't reach. James