From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Michal Such?nek <msuchanek@suse.de>,
David Hildenbrand <david@redhat.com>,
Gautham R Shenoy <ego@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 18:28:23 +0530 [thread overview]
Message-ID: <20200703125823.GA26243@linux.vnet.ibm.com> (raw)
In-Reply-To: <20200703105944.GS18446@dhcp22.suse.cz>
* Michal Hocko <mhocko@kernel.org> [2020-07-03 12:59:44]:
> > 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.
>
> Thinking about this some more, this logic makes some sense afterall.
> Especially in the world without memory hotplug which was very likely the
> case back then. It is much better to have compact node mask rather than
> sparse one. After all node numbers shouldn't really matter as long as
> you have a clear mapping to the HW. I am not sure we export that
> information (except for the kernel ring buffer) though.
>
> The memory hotplug changes that somehow because you can hotremove numa
> nodes and therefore make the nodemask sparse but that is not a common
> case. I am not sure what would happen if a completely new node was added
> and its corresponding node was already used by the renumbered one
> though. It would likely conflate the two I am afraid. But I am not sure
> this is really possible with x86 and a lack of a bug report would
> suggest that nobody is doing that at least.
>
JFYI,
Satheesh copied in this mailchain had opened a bug a year on crash with vcpu
hotplug on memoryless node.
https://bugzilla.kernel.org/show_bug.cgi?id=202187
--
Thanks and Regards
Srikar Dronamraju
next prev parent reply other threads:[~2020-07-03 12:59 UTC|newest]
Thread overview: 33+ 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
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 [this message]
2020-08-07 4:32 ` Andrew Morton
2020-08-07 6:58 ` David Hildenbrand
2020-08-07 10:04 ` Michal Suchánek
2020-08-12 6:01 ` Srikar Dronamraju
2020-08-18 7:32 ` David Hildenbrand
2020-08-18 7:37 ` Michal Hocko
2020-08-18 7:49 ` Srikar Dronamraju
2020-07-06 16:08 ` Andi Kleen
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