From: Srikar Dronamraju <email@example.com> To: David Hildenbrand <firstname.lastname@example.org> Cc: Michal Hocko <email@example.com>, Andrew Morton <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com, Mel Gorman <firstname.lastname@example.org>, Vlastimil Babka <email@example.com>, "Kirill A. Shutemov" <firstname.lastname@example.org>, Christopher Lameter <email@example.com>, Michael Ellerman <firstname.lastname@example.org>, Linus Torvalds <email@example.com>, Gautham R Shenoy <firstname.lastname@example.org>, Satheesh Rajendran <email@example.com> Subject: Re: [PATCH v5 3/3] mm/page_alloc: Keep memoryless cpuless node 0 offline Date: Wed, 1 Jul 2020 16:31:45 +0530 [thread overview] Message-ID: <20200701110145.GC17918@linux.vnet.ibm.com> (raw) In-Reply-To: <firstname.lastname@example.org> * David Hildenbrand <email@example.com> [2020-07-01 12:15:54]: > On 01.07.20 12:04, Srikar Dronamraju wrote: > > * Michal Hocko <firstname.lastname@example.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. > > Now, that is wrong. You get a memoryless/cpuless node, which is *not > online*. Once you hotplug some memory, it will switch online. Once you > remove memory, it will switch back offline. > Let me clarify, we are looking for a node 0 which is cpuless/memoryless at boot. The code in question tries to handle a cpuless/memoryless node 0 at boot. With the steps that you gave the node 0 was always populated, node 1 or some other node would be memoryless/cpuless and offline. But that should have no impact by patch. I don't see how adding/hotplugging/removing memory to a node after boot is going to affect the changes that I have made. Please do correct me if I have misunderstood. -- Thanks and Regards Srikar Dronamraju
next prev parent reply other threads:[~2020-07-01 11:02 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 [this message] 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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