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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 9BD5FC10F12 for ; Mon, 25 Mar 2019 14:50:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5AEF720811 for ; Mon, 25 Mar 2019 14:50:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553525429; bh=eqN51NDFbUAPg5+w5wr1VqKMf4COuFoP9GxRsWv3Ygk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=TNapSKDQ7HpHsWxqoTexxtD9exNhw+hZdHCuxfOBv3HBUdnNGXOMxScNSsOoeznua iMxqdSlJ4ByvSlV1oC0aYeOvjI7CjcNWYoooTZM6CB8+nWJ1bM+VFETurv0lBQ8EDd S+A2tfqFRor/3c3w8Wg206DMRaa9hj5Uk+uL+T9E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729389AbfCYOu2 (ORCPT ); Mon, 25 Mar 2019 10:50:28 -0400 Received: from mx2.suse.de ([195.135.220.15]:52448 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725788AbfCYOuZ (ORCPT ); Mon, 25 Mar 2019 10:50:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 058C5AF2F; Mon, 25 Mar 2019 14:50:23 +0000 (UTC) Date: Mon, 25 Mar 2019 15:50:23 +0100 From: Michal Hocko To: Jeff Moyer Cc: Dan Williams , Andrew Morton , =?iso-8859-1?B?Suly9G1l?= Glisse , Logan Gunthorpe , Toshi Kani , Vlastimil Babka , stable , Linux MM , linux-nvdimm , Linux Kernel Mailing List Subject: Re: [PATCH v5 00/10] mm: Sub-section memory hotplug support Message-ID: <20190325145023.GG9924@dhcp22.suse.cz> References: <155327387405.225273.9325594075351253804.stgit@dwillia2-desk3.amr.corp.intel.com> <20190322180532.GM32418@dhcp22.suse.cz> <20190325101945.GD9924@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 25-03-19 10:28:00, Jeff Moyer wrote: > Michal Hocko writes: > > >> > and I would like to know that you are > >> > not just shifting the problem to a smaller unit and a new/creative HW > >> > will force us to go even more complicated. > >> > >> HW will not do this to us. It's software that has the problem. > >> Namespace creation is unnecessarily constrained to 128MB alignment. > > > > And why is that a problem? A lack of documentation that this is a > > requirement? Something will not work with a larger alignment? Someting > > else? > > See this email for one user-visible problem: > https://lore.kernel.org/lkml/x49imxbx22d.fsf@segfault.boston.devel.redhat.com/ : # ndctl create-namespace -m fsdax -s 128m : Error: '--size=' must align to interleave-width: 6 and alignment: 2097152 : did you intend --size=132M? : : failed to create namespace: Invalid argument So the size is in section size units. So what prevents the userspace to use a proper alignment? I am sorry if this is a stupid question but I am not really familiar with ndctl nor the pmem side of it. -- Michal Hocko SUSE Labs