From: David Hildenbrand <david@redhat.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: akpm@linux-foundation.org, dan.j.williams@intel.com,
pasha.tatashin@soleen.com, mhocko@suse.com,
anshuman.khandual@arm.com, Jonathan.Cameron@huawei.com,
vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 0/5] Allocate memmap from hotadded memory
Date: Thu, 1 Aug 2019 10:44:35 +0200 [thread overview]
Message-ID: <9673cceb-afae-ae77-1bd8-56e07c814cc0@redhat.com> (raw)
In-Reply-To: <20190801083856.GA17316@linux>
On 01.08.19 10:39, Oscar Salvador wrote:
> On Thu, Aug 01, 2019 at 10:17:23AM +0200, David Hildenbrand wrote:
>> I am not yet sure about two things:
>>
>>
>> 1. Checking uninitialized pages for PageVmemmap() when onlining. I
>> consider this very bad.
>>
>> I wonder if it would be better to remember for each memory block the pfn
>> offset, which will be used when onlining/offlining.
>>
>> I have some patches that convert online_pages() to
>> __online_memory_block(struct memory block *mem) - which fits perfect to
>> the current user. So taking the offset and processing only these pages
>> when onlining would be easy. To do the same for offline_pages(), we
>> first have to rework memtrace code. But when offlining, all memmaps have
>> already been initialized.
>
> This is true, I did not really like that either, but was one of the things
> I came up.
> I already have some ideas how to avoid checking the page, I will work on it.
I think it would be best if we find some way that during
onlining/offlining we skip the vmemmap part completely. (e.g., as
discussed via an offset in the memblock or similar)
>
>> 2. Setting the Vmemmap pages to the zone of the online type. This would
>> mean we would have unmovable data on pages marked to belong to the
>> movable zone. I would suggest to always set them to the NORMAL zone when
>> onlining - and inititalize the vmemmap of the vmemmap pages directly
>> during add_memory() instead.
>
> IMHO, having vmemmap pages in ZONE_MOVABLE do not matter that match.
> They are not counted as managed_pages, and they are not show-stopper for
> moving all the other data around (migrate), they are just skipped.
> Conceptually, they are not pages we can deal with.
I am not sure yet about the implications of having these belong to a
zone they don't hmmmm. Will the pages be PG_reserved?
>
> I thought they should lay wherever the range lays.
> Having said that, I do not oppose to place them in ZONE_NORMAL, as they might
> fit there better under the theory that ZONE_NORMAL have memory that might not be
> movable/migratable.
>
> As for initializing them in add_memory(), we cannot do that.
> First problem is that we first need sparse_mem_map_populate to create
> the mapping, and to take the pages from our altmap.
>
> Then, we can access and initialize those pages.
> So we cannot do that in add_memory() because that happens before.
>
> And I really think that it fits much better in __add_pages than in add_memory.
Sorry, I rather meant when adding memory, not when onlining. But you
seem to do that already. :)
>
> Given said that, I would appreciate some comments in patches#3 and patches#4,
> specially patch#4.
Will have a look!
> So I would like to collect some feedback in those before sending a new version.
>
> Thanks David
>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2019-08-01 8:44 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-25 16:02 [PATCH v3 0/5] Allocate memmap from hotadded memory Oscar Salvador
2019-07-25 16:02 ` [PATCH v3 1/5] mm,memory_hotplug: Introduce MHP_MEMMAP_ON_MEMORY Oscar Salvador
2019-07-26 8:34 ` David Hildenbrand
2019-07-26 9:29 ` Oscar Salvador
2019-07-26 9:37 ` David Hildenbrand
2019-07-25 16:02 ` [PATCH v3 2/5] mm: Introduce a new Vmemmap page-type Oscar Salvador
2019-07-26 8:48 ` David Hildenbrand
2019-07-26 9:25 ` Oscar Salvador
2019-07-26 9:41 ` David Hildenbrand
2019-07-26 10:11 ` Oscar Salvador
2019-07-25 16:02 ` [PATCH v3 3/5] mm,sparse: Add SECTION_USE_VMEMMAP flag Oscar Salvador
2019-08-01 14:45 ` David Hildenbrand
2019-07-25 16:02 ` [PATCH v3 4/5] mm,memory_hotplug: Allocate memmap from the added memory range for sparse-vmemmap Oscar Salvador
2019-08-01 15:04 ` David Hildenbrand
2019-07-25 16:02 ` [PATCH v3 5/5] mm,memory_hotplug: Allow userspace to enable/disable vmemmap Oscar Salvador
2019-08-01 15:07 ` David Hildenbrand
2019-07-25 16:56 ` [PATCH v3 0/5] Allocate memmap from hotadded memory David Hildenbrand
2019-08-01 7:39 ` Oscar Salvador
2019-08-01 8:17 ` David Hildenbrand
2019-08-01 8:39 ` Oscar Salvador
2019-08-01 8:44 ` David Hildenbrand [this message]
2019-08-01 18:46 ` David Hildenbrand
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