From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
akpm@linux-foundation.org, mhocko@kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org, vbabka@suse.cz,
pasha.tatashin@soleen.com
Subject: Re: [PATCH 2/5] mm,memory_hotplug: Allocate memmap from the added memory range
Date: Mon, 25 Jan 2021 12:18:17 +0100 [thread overview]
Message-ID: <20210125111816.GB28363@linux> (raw)
In-Reply-To: <a0193441-4c79-b85e-ff38-e7ab3a462beb@redhat.com>
On Mon, Jan 25, 2021 at 11:57:20AM +0100, David Hildenbrand wrote:
> I'm confused.
>
> 1. Assume we hotplug memory, online it to ZONE_MOVABLE. The vmemmap gets
> allocated from altmap space.
The vmemmap could have never been allocated from altmap in case hpage vmemmap
feature is enabled.
Have a look at [1].
If is_hugetlb_free_vmemmap_enabled(), vmemmap_populate() ends up calling
vmemmap_populate_basepages().
And since no memory was consumed from altmap, and hence altmap_alloc_block_buf()
was never called, vmem_altmap->alloc will be 0, and memory_block->nr_vmemmap_pages
will be 0 as well.
But on a second though, true is that we will get in trouble if hpage vmemmap
feature ever gets to work with vmemmap_populate_hugepages.
I will queue that to look in a new future.
[1] https://patchwork.kernel.org/project/linux-mm/patch/20210117151053.24600-10-songmuchun@bytedance.com/
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2021-01-25 11:18 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 13:07 [PATCH 0/5] Allocate memmap from hotadded memory (per device) Oscar Salvador
2020-12-17 13:07 ` [PATCH 1/5] mm: Introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE Oscar Salvador
2021-01-11 16:52 ` David Hildenbrand
2021-01-12 7:26 ` Oscar Salvador
2021-01-12 10:12 ` David Hildenbrand
2021-01-12 11:17 ` Oscar Salvador
2021-01-12 11:17 ` David Hildenbrand
2020-12-17 13:07 ` [PATCH 2/5] mm,memory_hotplug: Allocate memmap from the added memory range Oscar Salvador
2021-01-18 10:11 ` Oscar Salvador
2021-01-19 13:58 ` David Hildenbrand
2021-01-25 10:39 ` Oscar Salvador
2021-01-25 10:56 ` Oscar Salvador
2021-01-25 11:02 ` David Hildenbrand
2021-01-25 13:36 ` Oscar Salvador
2021-01-25 10:57 ` David Hildenbrand
2021-01-25 11:18 ` Oscar Salvador [this message]
2021-01-25 11:23 ` David Hildenbrand
2020-12-17 13:07 ` [PATCH 3/5] acpi,memhotplug: Enable MHP_MEMMAP_ON_MEMORY when supported Oscar Salvador
2021-01-11 16:53 ` David Hildenbrand
2020-12-17 13:07 ` [PATCH 4/5] powerpc/memhotplug: " Oscar Salvador
2021-01-11 16:55 ` David Hildenbrand
2021-01-12 13:31 ` Oscar Salvador
2020-12-17 13:07 ` [PATCH 5/5] mm,memory_hotplug: Add kernel boot option to enable memmap_on_memory Oscar Salvador
2021-01-11 9:05 ` [PATCH 0/5] Allocate memmap from hotadded memory (per device) Oscar Salvador
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