Re: [PATCH 0/4] big chunk memory allocator v4

[Felipe Contreras]

On Fri, Nov 19, 2010 at 10:56 PM, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, 19 Nov 2010 17:10:33 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
>
>> Hi, this is an updated version.
>>
>> No major changes from the last one except for page allocation function.
>> removed RFC.
>>
>> Order of patches is
>>
>> [1/4] move some functions from memory_hotplug.c to page_isolation.c
>> [2/4] search physically contiguous range suitable for big chunk alloc.
>> [3/4] allocate big chunk memory based on memory hotplug(migration) technique
>> [4/4] modify page allocation function.
>>
>> For what:
>>
>> Â I hear there is requirements to allocate a chunk of page which is larger than
>> Â MAX_ORDER. Now, some (embeded) device use a big memory chunk. To use memory,
>> Â they hide some memory range by boot option (mem=) and use hidden memory
>> Â for its own purpose. But this seems a lack of feature in memory management.

Actually, now that's not needed any more by using memblock:
http://article.gmane.org/gmane.linux.ports.arm.omap/44978

>> Â This patch adds
>> Â Â Â alloc_contig_pages(start, end, nr_pages, gfp_mask)
>> Â to allocate a chunk of page whose length is nr_pages from [start, end)
>> Â phys address. This uses similar logic of memory-unplug, which tries to
>> Â offline [start, end) pages. By this, drivers can allocate 30M or 128M or
>> Â much bigger memory chunk on demand. (I allocated 1G chunk in my test).
>>
>> Â But yes, because of fragmentation, this cannot guarantee 100% alloc.
>> Â If alloc_contig_pages() is called in system boot up or movable_zone is used,
>> Â this allocation succeeds at high rate.
>
> So this is an alternatve implementation for the functionality offered
> by Michal's "The Contiguous Memory Allocator framework".
>
>> Â I tested this on x86-64, and it seems to work as expected. But feedback from
>> Â embeded guys are appreciated because I think they are main user of this
>> Â function.
>
> From where I sit, feedback from the embedded guys is *vital*, because
> they are indeed the main users.
>
> Michal, I haven't made a note of all the people who are interested in
> and who are potential users of this code. ÂYour patch series has a
> billion cc's and is up to version 6. ÂCould I ask that you review and
> test this code, and also hunt down other people (probably at other
> organisations) who can do likewise for us? ÂBecause until we hear from
> those people that this work satisfies their needs, we can't really
> proceed much further.

As I've explained before, a contiguous memory allocator would be nice,
but on ARM many drivers not only need contiguous memory, but
non-cacheable, and this requires removing the memory from normal
kernel mapping in early boot.

Cheers.

-- 
Felipe Contreras
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