From: David Hildenbrand <david@redhat.com>
To: Oscar Salvador <osalvador@suse.de>,
Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Vlastimil Babka <vbabka@suse.cz>, Linux MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/5] mm,memory_hotplug: Introduce MHP_VMEMMAP_FLAGS
Date: Thu, 25 Jul 2019 11:30:23 +0200 [thread overview]
Message-ID: <71a30086-b093-48a4-389f-7e407898718f@redhat.com> (raw)
In-Reply-To: <20190725092751.GA15964@linux>
On 25.07.19 11:27, Oscar Salvador wrote:
> On Wed, Jul 24, 2019 at 01:11:52PM -0700, Dan Williams wrote:
>> On Tue, Jun 25, 2019 at 12:53 AM Oscar Salvador <osalvador@suse.de> wrote:
>>>
>>> This patch introduces MHP_MEMMAP_DEVICE and MHP_MEMMAP_MEMBLOCK flags,
>>> and prepares the callers that add memory to take a "flags" parameter.
>>> This "flags" parameter will be evaluated later on in Patch#3
>>> to init mhp_restrictions struct.
>>>
>>> The callers are:
>>>
>>> add_memory
>>> __add_memory
>>> add_memory_resource
>>>
>>> Unfortunately, we do not have a single entry point to add memory, as depending
>>> on the requisites of the caller, they want to hook up in different places,
>>> (e.g: Xen reserve_additional_memory()), so we have to spread the parameter
>>> in the three callers.
>>>
>>> The flags are either MHP_MEMMAP_DEVICE or MHP_MEMMAP_MEMBLOCK, and only differ
>>> in the way they allocate vmemmap pages within the memory blocks.
>>>
>>> MHP_MEMMAP_MEMBLOCK:
>>> - With this flag, we will allocate vmemmap pages in each memory block.
>>> This means that if we hot-add a range that spans multiple memory blocks,
>>> we will use the beginning of each memory block for the vmemmap pages.
>>> This strategy is good for cases where the caller wants the flexiblity
>>> to hot-remove memory in a different granularity than when it was added.
>>>
>>> E.g:
>>> We allocate a range (x,y], that spans 3 memory blocks, and given
>>> memory block size = 128MB.
>>> [memblock#0 ]
>>> [0 - 511 pfns ] - vmemmaps for section#0
>>> [512 - 32767 pfns ] - normal memory
>>>
>>> [memblock#1 ]
>>> [32768 - 33279 pfns] - vmemmaps for section#1
>>> [33280 - 65535 pfns] - normal memory
>>>
>>> [memblock#2 ]
>>> [65536 - 66047 pfns] - vmemmap for section#2
>>> [66048 - 98304 pfns] - normal memory
>>>
>>> MHP_MEMMAP_DEVICE:
>>> - With this flag, we will store all vmemmap pages at the beginning of
>>> hot-added memory.
>>>
>>> E.g:
>>> We allocate a range (x,y], that spans 3 memory blocks, and given
>>> memory block size = 128MB.
>>> [memblock #0 ]
>>> [0 - 1533 pfns ] - vmemmap for section#{0-2}
>>> [1534 - 98304 pfns] - normal memory
>>>
>>> When using larger memory blocks (1GB or 2GB), the principle is the same.
>>>
>>> Of course, MHP_MEMMAP_DEVICE is nicer when it comes to have a large contigous
>>> area, while MHP_MEMMAP_MEMBLOCK allows us to have flexibility when removing the
>>> memory.
>>
>> Concept and patch looks good to me, but I don't quite like the
>> proliferation of the _DEVICE naming, in theory it need not necessarily
>> be ZONE_DEVICE that is the only user of that flag. I also think it
>> might be useful to assign a flag for the default 'allocate from RAM'
>> case, just so the code is explicit. So, how about:
>
> Well, MHP_MEMMAP_DEVICE is not tied to ZONE_DEVICE.
> MHP_MEMMAP_DEVICE was chosen to make a difference between:
>
> * allocate memmap pages for the whole memory-device
> * allocate memmap pages on each memoryblock that this memory-device spans
I agree that DEVICE is misleading here, you are assuming a one-to-one
mapping between a device and add_memory(). You are actually taliing
about "allocate a single chunk of mmap pages for the whole memory range
that is added - which could consist of multiple memory blocks".
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2019-07-25 9:30 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 7:52 [PATCH v2 0/5] Allocate memmap from hotadded memory Oscar Salvador
2019-06-25 7:52 ` [PATCH v2 1/5] drivers/base/memory: Remove unneeded check in remove_memory_block_devices Oscar Salvador
2019-06-25 8:01 ` David Hildenbrand
2019-06-25 8:03 ` David Hildenbrand
2019-06-25 8:09 ` Oscar Salvador
2019-06-25 8:27 ` David Hildenbrand
2019-06-25 7:52 ` [PATCH v2 2/5] mm,memory_hotplug: Introduce MHP_VMEMMAP_FLAGS Oscar Salvador
2019-06-25 8:31 ` David Hildenbrand
2019-07-24 20:11 ` Dan Williams
2019-07-24 21:36 ` osalvador
2019-07-25 9:27 ` Oscar Salvador
2019-07-25 9:30 ` David Hildenbrand [this message]
2019-07-25 9:40 ` Oscar Salvador
2019-07-25 10:04 ` David Hildenbrand
2019-07-25 10:13 ` Oscar Salvador
2019-07-25 10:15 ` David Hildenbrand
2019-06-25 7:52 ` [PATCH v2 3/5] mm,memory_hotplug: Introduce Vmemmap page helpers Oscar Salvador
2019-06-25 7:52 ` [PATCH v2 4/5] mm,memory_hotplug: allocate memmap from the added memory range for sparse-vmemmap Oscar Salvador
2019-06-25 8:49 ` David Hildenbrand
2019-06-26 8:13 ` Oscar Salvador
2019-06-26 8:15 ` David Hildenbrand
2019-06-26 8:17 ` Anshuman Khandual
2019-06-26 8:28 ` Oscar Salvador
2019-07-24 21:49 ` Dan Williams
2019-06-25 7:52 ` [PATCH v2 5/5] mm,memory_hotplug: Allow userspace to enable/disable vmemmap Oscar Salvador
2019-06-25 8:25 ` [PATCH v2 0/5] Allocate memmap from hotadded memory David Hildenbrand
2019-06-25 8:33 ` David Hildenbrand
2019-06-26 8:03 ` Oscar Salvador
2019-06-26 8:11 ` David Hildenbrand
2019-06-26 8:15 ` Oscar Salvador
2019-06-26 8:27 ` Oscar Salvador
2019-06-26 8:37 ` David Hildenbrand
2019-06-26 8:28 ` David Hildenbrand
2019-07-02 6:42 ` Rashmica Gupta
2019-07-02 7:48 ` Oscar Salvador
[not found] ` <CAC6rBskRyh5Tj9L-6T4dTgA18H0Y8GsMdC-X5_0Jh1SVfLLYtg@mail.gmail.com>
2019-07-10 1:14 ` Rashmica Gupta
2019-07-31 12:08 ` Michal Hocko
2019-07-31 23:06 ` Rashmica Gupta
2019-08-01 7:17 ` Michal Hocko
2019-08-01 7:18 ` David Hildenbrand
2019-08-01 7:24 ` Michal Hocko
2019-08-01 7:26 ` David Hildenbrand
2019-08-01 7:31 ` David Hildenbrand
2019-08-01 7:39 ` Michal Hocko
2019-08-01 7:48 ` Michal Hocko
2019-08-01 9:18 ` David Hildenbrand
2019-08-01 7:34 ` Michal Hocko
2019-08-01 7:50 ` David Hildenbrand
2019-08-01 8:04 ` Michal Hocko
2019-07-16 12:28 ` David Hildenbrand
2019-07-29 5:42 ` Rashmica Gupta
2019-07-29 8:06 ` David Hildenbrand
2019-07-30 7:08 ` Rashmica Gupta
2019-07-31 2:21 ` Rashmica Gupta
2019-07-31 9:39 ` David Hildenbrand
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