From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757892Ab0DIVhx (ORCPT ); Fri, 9 Apr 2010 17:37:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43246 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757893Ab0DIVhu (ORCPT ); Fri, 9 Apr 2010 17:37:50 -0400 Date: Fri, 9 Apr 2010 17:37:01 -0400 From: Jason Baron To: Masami Hiramatsu Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, mathieu.desnoyers@polymtl.ca, hpa@zytor.com, tglx@linutronix.de, rostedt@goodmis.org, andi@firstfloor.org, roland@redhat.com, rth@redhat.com, fweisbec@gmail.com, avi@redhat.com Subject: Re: [PATCH 0/9] jump label v6 Message-ID: <20100409213701.GC2774@redhat.com> References: <4BBF8FC8.9050707@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BBF8FC8.9050707@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 09, 2010 at 04:36:24PM -0400, Masami Hiramatsu wrote: > Hi Jason, > > Jason Baron wrote: > > Hi, > > > > Refresh of jump labeling patches aginst -tip tree. For bacground see: > > http://marc.info/?l=linux-kernel&m=125858436505941&w=2 > > > > I believe I've addressed all the reviews from v5. > > > > Changes in v6: > > > > * I've moved Steve Rostedt's 'ftrace_dyn_arch_init()' to alternative.c to > > put it into a common area for used by both ftrace and jump labels. By > > default we put a 'jmp 5' in the nop slot. Then, when we detect the best > > runtime no-op we patch over the 'jmp 5' with the appropriate nop. > > > > * build time sort of the jump label table. The jump label table is more > > optimally accessed if the entries are continguous. Sorting the table > > accomplishes this. Do the sort at build-time. Adds a '-j' option to > > 'modpost' which replaces the vmlinux, with a sorted jump label section vmlinux. > > I've tested this on x86 with relocatable and it works fine there as well. Note > > that I have not sorted the jump label table in modules. This is b/c the jump > > label names can be exported by the core kernel, and thus I don't have them > > available at buildtime. This could be solved by either finding the correct > > ones in the vmlinux, or by embedding the name of the jump label in the module > > tables (and not just a pointer), but the module tables tend to be smaller, and > > thus there is less value to this kind of change anyway. The kernel continues to > > do the sort, just in case, but at least for the vmlinux, this is just a > > verfication b/c the jump label table has already been sorted. > > > > * added jump_label_text_reserved(), so that other routines that want to patch > > the code, can first verify that they are not stomping on jump label addresses. > > Good!:-) > So now, it might be a good time to integrate those text_reserved() functions. > > BTW, how many jumps would you expect modifying at once? > Since the text_poke_smp() uses stop_machine() for each modifying text, > I found that it can cause a delay issue if it is called so many times... > (e.g. a systemtap testcase sets ~5000 probes at once) > > Thank you, > I'm counting 934 jump label locations in the vmlinux, i have compiled, 675 of them being 'kmalloc'. Batch mode for text_poke_smp()? -Jason