From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Vlastimil Babka <vbabka@suse.cz>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/5] mm,memory_hotplug: Allocate memmap from the added memory range
Date: Thu, 18 Mar 2021 13:03:59 +0100 [thread overview]
Message-ID: <YFNBrzNFpyKLORfe@localhost.localdomain> (raw)
In-Reply-To: <51c645b3-1220-80c4-e44c-4c0411222148@redhat.com>
On Thu, Mar 18, 2021 at 12:24:16PM +0100, David Hildenbrand wrote:
> I don't follow. 2MB == 2MB. And if there would be difference then we would
> be in the problem I brought up: vmemmap code allocating too much via the
> altmap, which can be very bad because might be populating more vmemmap than
> we actually need.
Yes, I meant to say nr_vmemmap_pages won't match, or IOW, won't have the
same meaning.
The end result is the same.
> vmemmap_size = 512 * 4KiB = 2 MiB.
>
> That calculation wasn't very useful (/ PAGE_SIZE * PAGE_SIZE)?
Yeah, somewhat redundant.
>
> > unsigned long remaining_size = size - vmemmap_size;
>
> And here we could get something like
>
> remaining_size = 2 GiB - 2 MiB
Yes, vmemmap_size would need to scale with nr_sections to be relative to
size.
Just wanted to bring it up, because somene might wonder
"ok, why do we have altmap->nr_pfns = X, and here nr_vmemmap_pages
is Y"
It was an effort to make it consistent, although I see it would bring
more confusion other than anything, so disregard.
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2021-03-18 12:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 17:55 [PATCH v4 0/5] Allocate memmap from hotadded memory (per device) Oscar Salvador
2021-03-09 17:55 ` [PATCH v4 1/5] mm,memory_hotplug: Allocate memmap from the added memory range Oscar Salvador
2021-03-11 19:06 ` David Hildenbrand
[not found] ` <20210315102224.GA24699@linux>
2021-03-16 16:46 ` David Hildenbrand
2021-03-16 17:45 ` David Hildenbrand
2021-03-17 14:08 ` Oscar Salvador
2021-03-17 14:35 ` David Hildenbrand
2021-03-18 8:27 ` Oscar Salvador
2021-03-18 10:38 ` Oscar Salvador
2021-03-18 11:24 ` David Hildenbrand
2021-03-18 12:03 ` Oscar Salvador [this message]
2021-03-18 12:05 ` David Hildenbrand
2021-03-09 17:55 ` [PATCH v4 2/5] acpi,memhotplug: Enable MHP_MEMMAP_ON_MEMORY when supported Oscar Salvador
2021-03-09 17:55 ` [PATCH v4 3/5] mm,memory_hotplug: Add kernel boot option to enable memmap_on_memory Oscar Salvador
2021-03-09 17:55 ` [PATCH v4 4/5] x86/Kconfig: Introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE Oscar Salvador
2021-03-09 17:55 ` [PATCH v4 5/5] arm64/Kconfig: " Oscar Salvador
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