From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932875AbbCROi0 (ORCPT ); Wed, 18 Mar 2015 10:38:26 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:43215 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932713AbbCROiY (ORCPT ); Wed, 18 Mar 2015 10:38:24 -0400 Date: Wed, 18 Mar 2015 15:38:04 +0100 From: Peter Zijlstra To: Christoph Hellwig Cc: mingo@kernel.org, rusty@rustcorp.com.au, mathieu.desnoyers@efficios.com, oleg@redhat.com, paulmck@linux.vnet.ibm.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, andi@firstfloor.org, rostedt@goodmis.org, tglx@linutronix.de Subject: Re: [PATCH 0/8] latched RB-trees and __module_address() Message-ID: <20150318143804.GN23123@twins.programming.kicks-ass.net> References: <20150318133626.526984618@infradead.org> <20150318142114.GA22761@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150318142114.GA22761@infradead.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 18, 2015 at 07:21:14AM -0700, Christoph Hellwig wrote: > On Wed, Mar 18, 2015 at 02:36:26PM +0100, Peter Zijlstra wrote: > > This series is aimed at making __module_address() go fast(er). > > What users do hit this so hard that it matters? Seems like the jump > label code uses it directly and throgh __module_text_address, and krobes > use it throug __module_text_address. Is it the pageattr code or > lockdep? >>From 7/8: "One of the users of this is kernel_text_address() which is employed in many stack unwinders; which in turn are used by perf-callchain and ftrace (possibly from NMI context). So by optimizing __module_address() we optimize many stack unwinders which are used by both perf and tracing in performance sensitive code." > Also seems interesting that both __module_address and __module_text_address > are exported, but don't seem to have modular users. Yeah and a few others too iirc.