From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754893Ab1I3P2J (ORCPT ); Fri, 30 Sep 2011 11:28:09 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:56785 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752560Ab1I3P2H (ORCPT ); Fri, 30 Sep 2011 11:28:07 -0400 X-Authority-Analysis: v=1.1 cv=lfM0d0QHaVz67dfwwr9cyIw6NbaGR/pZhMD6XWNi0kk= c=1 sm=0 a=eMQ7hR_6lG4A:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=17wjrS5wAhQaEczCPkpxpQ==:17 a=tHz9FfFoAAAA:8 a=ZPDoGCN9hik-CNn8tYgA:9 a=PUjeQqilurYA:10 a=6O0IECtVFhoA:10 a=17wjrS5wAhQaEczCPkpxpQ==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.83.30 Subject: Re: [PATCH RFC 0/8] jump-label: allow early jump_label_enable() From: Steven Rostedt To: Jeremy Fitzhardinge Cc: "David S. Miller" , David Daney , Michael Ellerman , Jan Glauber , Jason Baron , the arch/x86 maintainers , Xen Devel , Linux Kernel Mailing List , Jeremy Fitzhardinge Date: Fri, 30 Sep 2011 11:28:00 -0400 In-Reply-To: <4E854859.4020105@goop.org> References: <1317343975.4588.36.camel@gandalf.stny.rr.com> <4E854859.4020105@goop.org> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.0.3- Content-Transfer-Encoding: 7bit Message-ID: <1317396484.4588.52.camel@gandalf.stny.rr.com> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2011-09-29 at 21:40 -0700, Jeremy Fitzhardinge wrote: > On 09/29/2011 05:52 PM, Steven Rostedt wrote: > > On Thu, 2011-09-29 at 16:26 -0700, Jeremy Fitzhardinge wrote: > >> From: Jeremy Fitzhardinge > >> > >> One big question which arises is whether the _early() function is > >> necessary at all. All the stop_machine/mutex/etc stuff that > >> arch_jump_label_transform() ends up doing is redundant pre-SMP, but it > >> shouldn't hurt. Maybe we can just drop the _early function? It works > >> on x86, at least, because jump_label_enable() works, which uses the full > >> form. And dropping it would reduce this to a very much smaller series. > > It does slow down the boot process, which is not a good thing when > > everyone is pushing for the fastest restarts. > > Would it really though? stop_machine() doesn't do very much when there > are no other cpus. > > Not that I measured or anything, but there was no obvious big lag at boot. Just bringing up the point, but without measurements, its all hand waving. It may not be a big deal, and simpler code is always better if it doesn't harm anything else. > > > What we should probably do is have a global read_mostly variable called, > > smp_activated or something, then things that can be called before and > > after can read this variable to determine if it can skip certain > > protections. > > Could do that if it turns out to be a problem. > > > While we're at it, perhaps we could add a memory_initialized for things > > like tracers that want to trace early but need to wait till it can > > allocate buffers. If we had this flag, it could instead do an early > > memory init to create the buffers. > > That seems orthogonal to the jump_label changes. It is. But it's something that bugs me and this just reminded me of it ;) -- Steve