From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 19EEAC4CECE for ; Mon, 14 Oct 2019 19:20:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E462E21925 for ; Mon, 14 Oct 2019 19:20:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388369AbfJNTUx (ORCPT ); Mon, 14 Oct 2019 15:20:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46976 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728005AbfJNTUx (ORCPT ); Mon, 14 Oct 2019 15:20:53 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 39100307CDD1; Mon, 14 Oct 2019 19:20:53 +0000 (UTC) Received: from krava (ovpn-204-83.brq.redhat.com [10.40.204.83]) by smtp.corp.redhat.com (Postfix) with SMTP id EE8995D9CD; Mon, 14 Oct 2019 19:20:50 +0000 (UTC) Date: Mon, 14 Oct 2019 21:20:49 +0200 From: Jiri Olsa To: Andi Kleen Cc: Jiri Olsa , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Namhyung Kim , Alexander Shishkin , Peter Zijlstra , Michael Petlan Subject: Re: [PATCH 3/3] perf tools: Make 'struct map_shared' truly shared Message-ID: <20191014192049.GB15890@krava> References: <20191013151427.11941-1-jolsa@kernel.org> <20191013151427.11941-4-jolsa@kernel.org> <20191014031054.GJ9933@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191014031054.GJ9933@tassilo.jf.intel.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Mon, 14 Oct 2019 19:20:53 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 13, 2019 at 08:10:54PM -0700, Andi Kleen wrote: > On Sun, Oct 13, 2019 at 05:14:27PM +0200, Jiri Olsa wrote: > > Andi reported that maps cloning is eating lot of memory and > > it's probably unnecessary, because they keep the same data. > > > > Changing 'struct map_shared' to be a pointer inside 'struct map', > > so it can be shared on fork. Changing the map__clone function to > > actually share 'struct map_shared' for cloned maps. > > > > The 'struct map_shared' carries its own refcnt counter, which is > > incremented when it's assigned to new 'struct map' and decremented > > when 'struct map' gets deleted in map__delete (its refcnt is 0). > > > > This 'maps sharing' seems to save lot of heap for reports with > > many forks/cloned mmaps (over 60% in example below). > > The one case I wasn't sure about is with JIT support. So if > a map gets modified with fixup/start from /tmp/perf-%d > in one process, would it impact the other too? > > We may need a COW operation for this (hopefully rare) case. so the jitted mmaps are inserted into the data file and processed during report where they can overload existing maps - thats detected before addition in: thread__insert_map map_groups__fixup_overlappings - which uses COW way -> map__clone(map, false); to create new map other fixups to maps are being done only for kernel maps, where we dont have a problem, because there's only one copy jirka