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=-5.3 required=3.0 tests=BAYES_00, 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 E2D5BC5519F for ; Mon, 30 Nov 2020 08:51:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8CFEC2076E for ; Mon, 30 Nov 2020 08:51:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726560AbgK3IvG (ORCPT ); Mon, 30 Nov 2020 03:51:06 -0500 Received: from mx2.suse.de ([195.135.220.15]:34404 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725976AbgK3IvG (ORCPT ); Mon, 30 Nov 2020 03:51:06 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 21EE8AC95; Mon, 30 Nov 2020 08:50:25 +0000 (UTC) Date: Mon, 30 Nov 2020 09:50:22 +0100 From: Oscar Salvador To: Michal Hocko Cc: david@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, vbabka@suse.cz, pasha.tatashin@soleen.com Subject: Re: [RFC PATCH v2 3/4] mm,memory_hotplug: Add mhp_supports_memmap_on_memory Message-ID: <20201130085018.GA3825@linux> References: <20201125112048.8211-1-osalvador@suse.de> <20201125112048.8211-4-osalvador@suse.de> <20201127150253.GU31550@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201127150253.GU31550@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 27, 2020 at 04:02:53PM +0100, Michal Hocko wrote: > It should also require a tunable (kernel parameter for now but maybe we > will need a more fine grained control later) to enable this explicitly. > Earlier discussions have pointed out that allocating vmemmap from each > section can lead to a sparse memory unsuitable for very large pages. > So I believe this should be an opt in. Yeah, I already had that in mind, just did not get to implement it in this RFC yet as I was more focused on the implementation per se. I thought about a tunable in /sys/device/system/memory/[file], but a kernel command line boot option would also work and for the first implementation would be less for a hassel. > Also is there any reason why this cannot be a preparatory patch for the > actual implementation? It would look more natural that way to me. I guess you are right, will re-order it in a future submission. -- Oscar Salvador SUSE L3