From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754384AbdAZWT1 (ORCPT ); Thu, 26 Jan 2017 17:19:27 -0500 Received: from merlin.infradead.org ([205.233.59.134]:58790 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754366AbdAZWTZ (ORCPT ); Thu, 26 Jan 2017 17:19:25 -0500 Date: Thu, 26 Jan 2017 23:19:12 +0100 From: Peter Zijlstra To: Andres Freund Cc: eranian@gmail.com, LKML , Stephane Eranian , Arnaldo Carvalho de Melo , Jiri Olsa , Ingo Molnar , anton@ozlabs.org, Namhyung Kim Subject: Re: perf/jit doesn't cope well with mprotect() to jit containing pages Message-ID: <20170126221912.GF6515@twins.programming.kicks-ass.net> References: <20161210050218.jw4bak5jf766iqpb@alap3.anarazel.de> <20170126210052.3znejq6s4ah3l2ow@alap3.anarazel.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170126210052.3znejq6s4ah3l2ow@alap3.anarazel.de> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 26, 2017 at 01:00:52PM -0800, Andres Freund wrote: > The problem is that (quoted below) without that hack the subsequent > mmaps just expand the previous VMAs which leads to perf loosing its > (address,range) -> symbol mappings for previously (in the same expanded > range) known symbols. I'm assuming this is the userspace tool doing that, right? Acme, is that something we can cure? Instead of throwing away eveything known of the previous map, merge them when they grow? So I think the problem was that we don't track munmap(), so if you see two overlapping mappings, we have no clue and assume an munmap() has happened or something. I can't really remember, its been many many years since I wrote all that :-(