From: Vlastimil Babka <vbabka@suse.cz>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>, Mel Gorman <mgorman@suse.de>,
Mark <markk@clara.co.uk>, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Subject: Re: [RFC PATCH] mm: CONFIG_NR_ZONES_EXTENDED
Date: Tue, 1 Mar 2016 01:06:22 +0100 [thread overview]
Message-ID: <56D4DCFE.9040806@suse.cz> (raw)
In-Reply-To: <CAPcyv4i587ow4yEFN+81rd=_kVL3YV1daU7cDM4V4YCAhDMRVA@mail.gmail.com>
On 29.2.2016 18:55, Dan Williams wrote:
> On Mon, Feb 29, 2016 at 4:33 AM, Vlastimil Babka <vbabka@suse.cz> 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.
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next prev parent reply other threads:[~2016-03-01 0:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 6:19 [RFC PATCH] mm: CONFIG_NR_ZONES_EXTENDED Dan Williams
2016-02-02 5:42 ` Andrew Morton
2016-02-07 6:10 ` Dan Williams
2016-02-29 12:33 ` Vlastimil Babka
2016-02-29 17:55 ` Dan Williams
2016-03-01 0:06 ` Vlastimil Babka [this message]
2016-03-01 2:06 ` Dan Williams
2016-03-01 8:31 ` Vlastimil Babka
2016-03-01 23:43 ` Dan Williams
2016-03-02 8:10 ` Vlastimil Babka
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