From: Mike Rapoport <rppt@linux.ibm.com>
To: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
Michal Hocko <mhocko@kernel.org>, Jia He <justin.he@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Baoquan He <bhe@redhat.com>, Chuhong Yuan <hslester96@gmail.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Kaly Xin <Kaly.Xin@arm.com>
Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as EXPORT_SYMBOL_GPL
Date: Wed, 8 Jul 2020 11:39:51 +0300 [thread overview]
Message-ID: <20200708083951.GH386073@linux.ibm.com> (raw)
In-Reply-To: <999ea296-4695-1219-6a4d-a027718f61e5@redhat.com>
On Wed, Jul 08, 2020 at 10:26:41AM +0200, David Hildenbrand wrote:
> On 08.07.20 09:50, Dan Williams wrote:
> > On Wed, Jul 8, 2020 at 12:22 AM David Hildenbrand <david@redhat.com> wrote:
> >>
> >>>>>>>> On Tue 07-07-20 13:59:15, Jia He wrote:
> >>>>>>>>> This exports memory_add_physaddr_to_nid() for module driver to use.
> >>>>>>>>>
> >>>>>>>>> memory_add_physaddr_to_nid() is a fallback option to get the nid in case
> >>>>>>>>> NUMA_NO_NID is detected.
> >>>>>>>>>
> >>>>>>>>> Suggested-by: David Hildenbrand <david@redhat.com>
> >>>>>>>>> Signed-off-by: Jia He <justin.he@arm.com>
> >>>>>>>>> ---
> >>>>>>>>> arch/arm64/mm/numa.c | 5 +++--
> >>>>>>>>> 1 file changed, 3 insertions(+), 2 deletions(-)
> >>>>>>>>>
> >>>>>>>>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> >>>>>>>>> index aafcee3e3f7e..7eeb31740248 100644
> >>>>>>>>> --- a/arch/arm64/mm/numa.c
> >>>>>>>>> +++ b/arch/arm64/mm/numa.c
> >>>>>>>>> @@ -464,10 +464,11 @@ void __init arm64_numa_init(void)
> >>>>>>>>>
> >>>>>>>>> /*
> >>>>>>>>> * We hope that we will be hotplugging memory on nodes we already know about,
> >>>>>>>>> - * such that acpi_get_node() succeeds and we never fall back to this...
> >>>>>>>>> + * such that acpi_get_node() succeeds. But when SRAT is not present, the node
> >>>>>>>>> + * id may be probed as NUMA_NO_NODE by acpi, Here provide a fallback option.
> >>>>>>>>> */
> >>>>>>>>> int memory_add_physaddr_to_nid(u64 addr)
> >>>>>>>>> {
> >>>>>>>>> - pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr);
> >>>>>>>>> return 0;
> >>>>>>>>> }
> >>>>>>>>> +EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
> >>>>>>>>
> >>>>>>>> Does it make sense to export a noop function? Wouldn't make more sense
> >>>>>>>> to simply make it static inline somewhere in a header? I haven't checked
> >>>>>>>> whether there is an easy way to do that sanely bu this just hit my eyes.
> I'd be curious if what we are trying to optimize here is actually worth
> optimizing. IOW, is there a well-known scenario where the dummy value on
> arm64 would be problematic and is worth the effort?
Well, it started with Michal's comment above that EXPORT_SYMBOL_GPL()
for a stub might be an overkill.
I think Jia's suggestion [1] with addition of a comment that explains
why and when the stub will be used, can work for both
memory_add_physaddr_to_nid() and phys_to_target_node().
But on more theoretical/fundmanetal level, I think we lack a generic
abstraction similar to e.g. x86 'struct numa_meminfo' that serves as
translaton of firmware supplied information into data that can be used
by the generic mm without need to reimplement it for each and every
arch.
[1] https://lore.kernel.org/lkml/AM6PR08MB406907F9F2B13DA6DC893AD9F7670@AM6PR08MB4069.eurprd08.prod.outlook.com
> I mean, in all performance relevant setups (ignoring
> hv_balloon/xen-balloon/prove_store(), which also use
> memory_add_physaddr_to_nid()), we should have a proper PXM/node
> specified by the hardware on memory hotadd. The fallback of
> memory_add_physaddr_to_nid() is not relevant in these scenarios.
>
> --
> Thanks,
>
> David / dhildenb
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2020-07-08 8:40 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 5:59 [PATCH v2 0/3] Fix and enable pmem as RAM device on arm64 Jia He
2020-07-07 5:59 ` [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as EXPORT_SYMBOL_GPL Jia He
2020-07-07 11:35 ` David Hildenbrand
2020-07-07 11:54 ` Michal Hocko
2020-07-07 12:13 ` Mike Rapoport
2020-07-07 12:26 ` David Hildenbrand
2020-07-07 18:00 ` Mike Rapoport
2020-07-07 22:05 ` Dan Williams
2020-07-08 5:27 ` Mike Rapoport
2020-07-08 7:21 ` David Hildenbrand
2020-07-08 7:38 ` Mike Rapoport
2020-07-08 7:40 ` David Hildenbrand
2020-07-08 7:50 ` Dan Williams
2020-07-08 8:26 ` David Hildenbrand
2020-07-08 8:39 ` Mike Rapoport [this message]
2020-07-08 8:45 ` David Hildenbrand
2020-07-08 9:15 ` Mike Rapoport
2020-07-08 9:25 ` David Hildenbrand
2020-07-08 9:45 ` Mike Rapoport
2020-07-08 10:04 ` David Hildenbrand
2020-07-08 15:50 ` Dan Williams
2020-07-08 16:10 ` David Hildenbrand
2020-07-08 16:47 ` Mike Rapoport
2020-07-08 2:20 ` Justin He
2020-07-08 3:56 ` Dan Williams
2020-07-08 4:08 ` Justin He
2020-07-08 4:27 ` Dan Williams
2020-07-08 6:22 ` Mike Rapoport
2020-07-08 6:53 ` Dan Williams
2020-07-08 6:59 ` David Hildenbrand
2020-07-08 7:04 ` Dan Williams
2020-07-08 7:16 ` David Hildenbrand
2020-07-08 7:43 ` Mike Rapoport
2020-07-08 5:32 ` Mike Rapoport
2020-07-08 5:48 ` Dan Williams
2020-07-08 6:19 ` Mike Rapoport
2020-07-08 6:44 ` Dan Williams
2020-07-08 6:56 ` Justin He
2020-07-08 7:00 ` David Hildenbrand
2020-07-07 5:59 ` [RFC PATCH v2 2/3] device-dax: use fallback nid when numa_node is invalid Jia He
2020-07-07 6:08 ` Justin He
2020-07-07 11:34 ` David Hildenbrand
2020-07-08 1:41 ` Justin He
2020-07-07 5:59 ` [PATCH v2 3/3] mm/memory_hotplug: fix unpaired mem_hotplug_begin/done Jia He
2020-07-07 10:06 ` Michal Hocko
2020-07-07 11:31 ` David Hildenbrand
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