From: David Hildenbrand <david@redhat.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
VlastimilBabkavbabka@suse.cz, pasha.tatashin@soleen.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Anshuman Khandual <anshuman.khandual@arm.com>
Subject: Re: [PATCH v2 6/7] x86/Kconfig: Introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
Date: Mon, 1 Mar 2021 09:45:07 +0100 [thread overview]
Message-ID: <de1e2213-7dea-da52-607b-d4d718a3e04e@redhat.com> (raw)
In-Reply-To: <20210226120451.GA3661@localhost.localdomain>
On 26.02.21 13:04, Oscar Salvador wrote:
> On Thu, Feb 25, 2021 at 07:29:07PM +0100, David Hildenbrand wrote:
>> On 09.02.21 14:38, Oscar Salvador wrote:
>>> Enable x86_64 platform to use the MHP_MEMMAP_ON_MEMORY feature.
>>>
>>> Signed-off-by: Oscar Salvador <osalvador@suse.de>
>>> ---
>>> arch/x86/Kconfig | 4 ++++
>>> 1 file changed, 4 insertions(+)
>>>
>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>>> index 72663de8b04c..81046b7adb10 100644
>>> --- a/arch/x86/Kconfig
>>> +++ b/arch/x86/Kconfig
>>> @@ -2440,6 +2440,10 @@ config ARCH_ENABLE_MEMORY_HOTREMOVE
>>> def_bool y
>>> depends on MEMORY_HOTPLUG
>>> +config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
>>> + def_bool y
>>> + depends on X86_64 && MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP_ENABLE
>>
>> It depends on SPARSEMEM_VMEMMAP, no?
>>
>> I think we could have
>>
>> SPARSEMEM_VMEMMAP_ENABLE=y
>> and
>> SPARSEMEM_VMEMMAP=n
>>
>> on manually tuned configs.
>
> I do not think this can happen:
>
> from mm/Kconfig:
>
> config SPARSEMEM_VMEMMAP_ENABLE
> bool
>
> config SPARSEMEM_VMEMMAP
> bool "Sparse Memory virtual memmap"
> depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
> default y
> help
> SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
> pfn_to_page and page_to_pfn operations. This is the most
> efficient option when sufficient kernel resources are available
>
> and from arch/x86/Kconfig:
>
> config ARCH_SPARSEMEM_ENABLE
> def_bool y
> depends on X86_64 || NUMA || X86_32 || X86_32_NON_STANDARD
> select SPARSEMEM_STATIC if X86_32
> select SPARSEMEM_VMEMMAP_ENABLE if X86_64
>
>
> So, if I read this correctly, for SPARSEMEM_VMEMMAP to be true,
> SPARSEMEM_VMEMMAP_ENABLE needs to be true as well.
>
> Am I missing something?
Take your config and set
X86_5LEVEL=n
(because it enforces SPARSEMEM_VMEMMAP)
and
SPARSEMEM_VMEMMAP=n
When compiling, you'll end up with a config like
CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
# CONFIG_SPARSEMEM_VMEMMAP is not set
Yet, with your patch you would get
ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE=y
And it would not get fenced off in the code, right?
I think you either have to check (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP))
in addition in your code, or enforce it differently. Like
config MHP_MEMMAP_ON_MEMORY
depends on SPARSEMEM_VMEMMAP && ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
bool
Then you can simplify the arch Kconfig settings, removing the sparesemem
dependency there.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-03-01 8:45 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 13:38 [PATCH v2 0/7] Allocate memmap from hotadded memory (per device) Oscar Salvador
2021-02-09 13:38 ` [PATCH v2 1/7] mm,memory_hotplug: Allocate memmap from the added memory range Oscar Salvador
2021-02-25 18:58 ` David Hildenbrand
2021-02-28 18:50 ` Oscar Salvador
2021-03-01 8:30 ` David Hildenbrand
2021-03-01 8:32 ` David Hildenbrand
2021-02-09 13:38 ` [PATCH v2 2/7] acpi,memhotplug: Enable MHP_MEMMAP_ON_MEMORY when supported Oscar Salvador
2021-02-09 13:38 ` [PATCH v2 3/7] mm,memory_hotplug: Add kernel boot option to enable memmap_on_memory Oscar Salvador
2021-02-25 18:25 ` David Hildenbrand
2021-02-26 12:14 ` Oscar Salvador
2021-03-01 8:27 ` David Hildenbrand
2021-02-09 13:38 ` [PATCH v2 4/7] mm,memory_hotplug: Enforce struct page size to be multiple of PMD Oscar Salvador
2021-02-25 18:26 ` David Hildenbrand
2021-02-26 12:06 ` Oscar Salvador
2021-03-01 10:06 ` Oscar Salvador
2021-03-01 10:24 ` David Hildenbrand
2021-02-09 13:38 ` [PATCH v2 5/7] mm,memory_hotplug: Enforce pageblock alignment when memmap_on_memory Oscar Salvador
2021-02-25 18:27 ` David Hildenbrand
2021-02-26 12:06 ` Oscar Salvador
2021-02-09 13:38 ` [PATCH v2 6/7] x86/Kconfig: Introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE Oscar Salvador
2021-02-25 18:29 ` David Hildenbrand
2021-02-26 12:04 ` Oscar Salvador
2021-03-01 8:45 ` David Hildenbrand [this message]
2021-03-01 10:07 ` Oscar Salvador
2021-02-09 13:38 ` [PATCH v2 7/7] arm64/Kconfig: " Oscar Salvador
2021-02-25 18:29 ` David Hildenbrand
2021-02-26 12:10 ` Oscar Salvador
2021-02-17 10:18 ` [PATCH v2 0/7] Allocate memmap from hotadded memory (per device) Oscar Salvador
2021-02-22 11:15 ` Oscar Salvador
2021-02-22 11:28 ` David Hildenbrand
2021-02-23 7:48 ` Oscar Salvador
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