From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
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 11:40:34 +0200 [thread overview]
Message-ID: <20190725094030.GA16069@linux> (raw)
In-Reply-To: <71a30086-b093-48a4-389f-7e407898718f@redhat.com>
On Thu, Jul 25, 2019 at 11:30:23AM +0200, David Hildenbrand wrote:
> 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".
Well, I could not come up with a better name.
MHP_MEMMAP_ALL?
MHP_MEMMAP_WHOLE?
I will send v3 shortly and then we can think of a better name.
>
> --
>
> Thanks,
>
> David / dhildenb
>
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2019-07-25 9:40 UTC|newest]
Thread overview: 58+ 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
2019-07-25 9:40 ` Oscar Salvador [this message]
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 10:28 ` David Hildenbrand
2019-06-26 9:48 ` 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
2019-07-02 8:52 ` Rashmica Gupta
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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