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From: Michal Hocko <mhocko@kernel.org>
To: "Michal Suchánek" <msuchanek@suse.de>
Cc: David Hildenbrand <david@redhat.com>,
	Gautham R Shenoy <ego@linux.vnet.ibm.com>,
	Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>,
	Mel Gorman <mgorman@suse.de>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Andrew Morton <akpm@linux-foundation.org>,
	linuxppc-dev@lists.ozlabs.org, Christopher Lameter <cl@linux.com>,
	Vlastimil Babka <vbabka@suse.cz>, Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v5 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline
Date: Fri, 3 Jul 2020 11:24:14 +0200
Message-ID: <20200703092414.GR18446@dhcp22.suse.cz> (raw)
In-Reply-To: <20200703091001.GJ21462@kitsune.suse.cz>

[Cc Andi]

On Fri 03-07-20 11:10:01, Michal Suchanek wrote:
> On Wed, Jul 01, 2020 at 02:21:10PM +0200, Michal Hocko wrote:
> > On Wed 01-07-20 13:30:57, David Hildenbrand wrote:
[...]
> > > Yep, looks like it.
> > > 
> > > [    0.009726] SRAT: PXM 1 -> APIC 0x00 -> Node 0
> > > [    0.009727] SRAT: PXM 1 -> APIC 0x01 -> Node 0
> > > [    0.009727] SRAT: PXM 1 -> APIC 0x02 -> Node 0
> > > [    0.009728] SRAT: PXM 1 -> APIC 0x03 -> Node 0
> > > [    0.009731] ACPI: SRAT: Node 0 PXM 1 [mem 0x00000000-0x0009ffff]
> > > [    0.009732] ACPI: SRAT: Node 0 PXM 1 [mem 0x00100000-0xbfffffff]
> > > [    0.009733] ACPI: SRAT: Node 0 PXM 1 [mem 0x100000000-0x13fffffff]
> > 
> > This begs a question whether ppc can do the same thing?
> Or x86 stop doing it so that you can see on what node you are running?
> 
> What's the point of this indirection other than another way of avoiding
> empty node 0?

Honestly, I do not have any idea. I've traced it down to
Author: Andi Kleen <ak@suse.de>
Date:   Tue Jan 11 15:35:48 2005 -0800

    [PATCH] x86_64: Fix ACPI SRAT NUMA parsing

    Fix fallout from the recent nodemask_t changes. The node ids assigned
    in the SRAT parser were off by one.

    I added a new first_unset_node() function to nodemask.h to allocate
    IDs sanely.

    Signed-off-by: Andi Kleen <ak@suse.de>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>

which doesn't really tell all that much. The historical baggage and a
long term behavior which is not really trivial to fix I suspect.
-- 
Michal Hocko
SUSE Labs


  reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-24  9:28 [PATCH v5 0/3] Offline memoryless cpuless node 0 Srikar Dronamraju
2020-06-24  9:28 ` [PATCH v5 1/3] powerpc/numa: Set numa_node for all possible cpus Srikar Dronamraju
2020-06-24  9:48   ` Gautham R Shenoy
2020-06-24  9:28 ` [PATCH v5 2/3] powerpc/numa: Prefer node id queried from vphn Srikar Dronamraju
2020-06-24 10:29   ` Gautham R Shenoy
2020-06-24  9:28 ` [PATCH v5 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline Srikar Dronamraju
2020-06-29 14:58   ` Christopher Lameter
2020-06-30  4:01     ` Srikar Dronamraju
2020-07-01 12:23       ` Michal Hocko
2020-07-01  8:42   ` Michal Hocko
2020-07-01 10:04     ` Srikar Dronamraju
2020-07-01 10:15       ` David Hildenbrand
2020-07-01 11:01         ` Srikar Dronamraju
2020-07-01 11:06           ` David Hildenbrand
2020-07-01 11:30             ` David Hildenbrand
2020-07-01 12:21               ` Michal Hocko
2020-07-02  6:44                 ` Srikar Dronamraju
2020-07-02  8:41                   ` Michal Hocko
2020-07-02 14:32                     ` Srikar Dronamraju
2020-07-03  9:10                 ` Michal Suchánek
2020-07-03  9:24                   ` Michal Hocko [this message]
2020-07-03 10:59                     ` Michal Hocko
2020-07-03 11:32                       ` David Hildenbrand
2020-07-03 11:46                         ` Michal Hocko
2020-07-03 12:58                       ` Srikar Dronamraju
2020-08-07  4:32                         ` Andrew Morton
2020-08-07  6:58                           ` David Hildenbrand
2020-08-07 10:04                             ` Michal Suchánek
2020-07-06 16:08                     ` Andi Kleen

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