From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f52.google.com (mail-wm0-f52.google.com [74.125.82.52]) by kanga.kvack.org (Postfix) with ESMTP id B06F86B0009 for ; Mon, 29 Feb 2016 19:06:23 -0500 (EST) Received: by mail-wm0-f52.google.com with SMTP id l68so11619277wml.1 for ; Mon, 29 Feb 2016 16:06:23 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id km9si34485748wjb.149.2016.02.29.16.06.22 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 29 Feb 2016 16:06:22 -0800 (PST) Subject: Re: [RFC PATCH] mm: CONFIG_NR_ZONES_EXTENDED References: <20160128061914.32541.97351.stgit@dwillia2-desk3.amr.corp.intel.com> <20160201214213.2bdf9b4e.akpm@linux-foundation.org> <56D43AAB.2010802@suse.cz> From: Vlastimil Babka Message-ID: <56D4DCFE.9040806@suse.cz> Date: Tue, 1 Mar 2016 01:06:22 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: Andrew Morton , Rik van Riel , Dave Hansen , "linux-kernel@vger.kernel.org" , Linux MM , Mel Gorman , Mark , Joonsoo Kim , Sudip Mukherjee 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: >>> So if you want ZONE_DMA, you're limited to 512 NUMA nodes? >>> >>> That seems reasonable. >> >> >> Sorry for the late reply, but it seems that with !SPARSEMEM, or with >> SPARSEMEM_VMEMMAP, reducing NUMA nodes isn't even necessary, because >> SECTIONS_WIDTH is zero (see the diagrams in linux/page-flags-layout.h). In >> my brief tests with 4.4 based kernel with SPARSEMEM_VMEMMAP it seems that >> with 1024 NUMA nodes and 8192 CPU's, there's still 7 bits left (i.e. 6 with >> CONFIG_NR_ZONES_EXTENDED). >> >> With the danger of becoming even more complex, could the limit also depend >> on CONFIG_SPARSEMEM/VMEMMAP to reflect that somehow? > > 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. -- 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