From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>,
David Hildenbrand <david@redhat.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>
Subject: Re: [PATCH v5 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline
Date: Wed, 1 Jul 2020 15:34:42 +0530 [thread overview]
Message-ID: <20200701100442.GB17918@linux.vnet.ibm.com> (raw)
In-Reply-To: <20200701084200.GN2369@dhcp22.suse.cz>
* Michal Hocko <mhocko@kernel.org> [2020-07-01 10:42:00]:
>
> >
> > 2. Also existence of dummy node also leads to inconsistent information. The
> > number of online nodes is inconsistent with the information in the
> > device-tree and resource-dump
> >
> > 3. When the dummy node is present, single node non-Numa systems end up showing
> > up as NUMA systems and numa_balancing gets enabled. This will mean we take
> > the hit from the unnecessary numa hinting faults.
>
> I have to say that I dislike the node online/offline state and directly
> exporting that to the userspace. Users should only care whether the node
> has memory/cpus. Numa nodes can be online without any memory. Just
> offline all the present memory blocks but do not physically hot remove
> them and you are in the same situation. If users are confused by an
> output of tools like numactl -H then those could be updated and hide
> nodes without any memory&cpus.
>
> The autonuma problem sounds interesting but again this patch doesn't
> really solve the underlying problem because I strongly suspect that the
> problem is still there when a numa node gets all its memory offline as
> mentioned above.
>
> While I completely agree that making node 0 special is wrong, I have
> still hard time to review this very simply looking patch because all the
> numa initialization is so spread around that this might just blow up
> at unexpected places. IIRC we have discussed testing in the previous
> version and David has provided a way to emulate these configurations
> on x86. Did you manage to use those instruction for additional testing
> on other than ppc architectures?
>
I have tried all the steps that David mentioned and reported back at
https://lore.kernel.org/lkml/20200511174731.GD1961@linux.vnet.ibm.com/t/#u
As a summary, David's steps are still not creating a memoryless/cpuless on
x86 VM. I have tried booting with Numa/non-numa on all the x86 machines that
I could get to.
--
Thanks and Regards
Srikar Dronamraju
next prev parent reply other threads:[~2020-07-01 10:14 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 [this message]
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
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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