From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752083AbcCAXno (ORCPT ); Tue, 1 Mar 2016 18:43:44 -0500 Received: from mail-ob0-f169.google.com ([209.85.214.169]:34948 "EHLO mail-ob0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750843AbcCAXnm (ORCPT ); Tue, 1 Mar 2016 18:43:42 -0500 MIME-Version: 1.0 In-Reply-To: <56D55359.3080809@suse.cz> References: <20160128061914.32541.97351.stgit@dwillia2-desk3.amr.corp.intel.com> <20160201214213.2bdf9b4e.akpm@linux-foundation.org> <56D43AAB.2010802@suse.cz> <56D4DCFE.9040806@suse.cz> <56D55359.3080809@suse.cz> Date: Tue, 1 Mar 2016 15:43:41 -0800 Message-ID: Subject: Re: [RFC PATCH] mm: CONFIG_NR_ZONES_EXTENDED From: Dan Williams To: Vlastimil Babka Cc: Andrew Morton , Rik van Riel , Dave Hansen , "linux-kernel@vger.kernel.org" , Linux MM , Mel Gorman , Mark , Joonsoo Kim , Sudip Mukherjee Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 1, 2016 at 12:31 AM, Vlastimil Babka wrote: > On 03/01/2016 03:06 AM, Dan Williams wrote: >> >> On Mon, Feb 29, 2016 at 4:06 PM, Vlastimil Babka wrote: >>> >>> On 29.2.2016 18:55, Dan Williams wrote: >>>> >>>> On Mon, Feb 29, 2016 at 4:33 AM, Vlastimil Babka wrote: >>>>> >>>>> On 02/02/2016 06:42 AM, Andrew Morton wrote: >>>> >>>> >>>> In this case it's already part of the equation because: >>>> >>>> config ZONE_DEVICE >>>> depends on MEMORY_HOTPLUG >>>> depends on MEMORY_HOTREMOVE >>>> >>>> ...and those in turn depend on SPARSEMEM. >>> >>> >>> Fine, but then SPARSEMEM_VMEMMAP should be still an available subvariant >>> of >>> SPARSEMEM with SECTION_WIDTH=0. >> >> >> It should be, but not for the ZONE_DEVICE case. ZONE_DEVICE depends >> on x86_64 which means ZONE_DEVICE also implies SPARSEMEM_VMEMMAP >> since: >> >> config ARCH_SPARSEMEM_ENABLE >> def_bool y >> depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD >> select SPARSEMEM_STATIC if X86_32 >> select SPARSEMEM_VMEMMAP_ENABLE if X86_64 >> >> Now, if a future patch wants to reclaim page flags space for other >> usages outside of ZONE_DEVICE it can do the work to handle the >> SPARSEMEM_VMEMMAP=n case. I don't see a reason to fold that >> distinction into the current patch given the current constraints. > > > OK so that IUUC shows that x86_64 should be always fine without decreasing > the range for NODES_SHIFT? That's basically my point - since there's a > configuration where things don't fit (32bit?), the patch broadly decreases > range for NODES_SHIFT for everyone, right? So I went hunting for the x86_64 config that sent me off in this direction in the first place, but I can't reproduce it. I'm indeed able to fit ZONE_DEVICE + ZONE_DMA + NODES_SHIFT(10) without overflowing page flags. Maybe we reduced some usage page->flags usage between 4.3 and 4.5 and I missed it? In any event, you're right we can indeed fit ZONE_DEVICE into the current MAXSMP definition. I'll respin the patch. Thanks for probing on this! From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f49.google.com (mail-oi0-f49.google.com [209.85.218.49]) by kanga.kvack.org (Postfix) with ESMTP id C5B126B0009 for ; Tue, 1 Mar 2016 18:43:42 -0500 (EST) Received: by mail-oi0-f49.google.com with SMTP id m82so141445895oif.1 for ; Tue, 01 Mar 2016 15:43:42 -0800 (PST) Received: from mail-ob0-x22d.google.com (mail-ob0-x22d.google.com. [2607:f8b0:4003:c01::22d]) by mx.google.com with ESMTPS id q203si27209389oih.142.2016.03.01.15.43.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 01 Mar 2016 15:43:42 -0800 (PST) Received: by mail-ob0-x22d.google.com with SMTP id rt7so10792713obb.3 for ; Tue, 01 Mar 2016 15:43:41 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <56D55359.3080809@suse.cz> References: <20160128061914.32541.97351.stgit@dwillia2-desk3.amr.corp.intel.com> <20160201214213.2bdf9b4e.akpm@linux-foundation.org> <56D43AAB.2010802@suse.cz> <56D4DCFE.9040806@suse.cz> <56D55359.3080809@suse.cz> Date: Tue, 1 Mar 2016 15:43:41 -0800 Message-ID: Subject: Re: [RFC PATCH] mm: CONFIG_NR_ZONES_EXTENDED From: Dan Williams Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Andrew Morton , Rik van Riel , Dave Hansen , "linux-kernel@vger.kernel.org" , Linux MM , Mel Gorman , Mark , Joonsoo Kim , Sudip Mukherjee On Tue, Mar 1, 2016 at 12:31 AM, Vlastimil Babka wrote: > On 03/01/2016 03:06 AM, Dan Williams wrote: >> >> On Mon, Feb 29, 2016 at 4:06 PM, Vlastimil Babka wrote: >>> >>> On 29.2.2016 18:55, Dan Williams wrote: >>>> >>>> On Mon, Feb 29, 2016 at 4:33 AM, Vlastimil Babka wrote: >>>>> >>>>> On 02/02/2016 06:42 AM, Andrew Morton wrote: >>>> >>>> >>>> In this case it's already part of the equation because: >>>> >>>> config ZONE_DEVICE >>>> depends on MEMORY_HOTPLUG >>>> depends on MEMORY_HOTREMOVE >>>> >>>> ...and those in turn depend on SPARSEMEM. >>> >>> >>> Fine, but then SPARSEMEM_VMEMMAP should be still an available subvariant >>> of >>> SPARSEMEM with SECTION_WIDTH=0. >> >> >> It should be, but not for the ZONE_DEVICE case. ZONE_DEVICE depends >> on x86_64 which means ZONE_DEVICE also implies SPARSEMEM_VMEMMAP >> since: >> >> config ARCH_SPARSEMEM_ENABLE >> def_bool y >> depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD >> select SPARSEMEM_STATIC if X86_32 >> select SPARSEMEM_VMEMMAP_ENABLE if X86_64 >> >> Now, if a future patch wants to reclaim page flags space for other >> usages outside of ZONE_DEVICE it can do the work to handle the >> SPARSEMEM_VMEMMAP=n case. I don't see a reason to fold that >> distinction into the current patch given the current constraints. > > > OK so that IUUC shows that x86_64 should be always fine without decreasing > the range for NODES_SHIFT? That's basically my point - since there's a > configuration where things don't fit (32bit?), the patch broadly decreases > range for NODES_SHIFT for everyone, right? So I went hunting for the x86_64 config that sent me off in this direction in the first place, but I can't reproduce it. I'm indeed able to fit ZONE_DEVICE + ZONE_DMA + NODES_SHIFT(10) without overflowing page flags. Maybe we reduced some usage page->flags usage between 4.3 and 4.5 and I missed it? In any event, you're right we can indeed fit ZONE_DEVICE into the current MAXSMP definition. I'll respin the patch. Thanks for probing on this! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org