Hugepages for shm page cache (defrag)

["Radosław Smogura" <mail@smogura.eu>]

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Hello,

This is may first try with Linux patch, so please do not blame me too much. 
Actually I started with small idea to add MAP_HUGTLB for /dev/shm but it grew 
up in something more like support for huge pages in page cache, but according 
to documentation to submit alpha-work too, I decided to send this.

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Idea is that I created defrag method which tries to defragment page cache to 
huge page, I added one flag for such compound page, as I want to treat it 
little different, for example any put/get unless/test zero will increase it 
count, so page will be freed if all "sub-pages" will be freed. From other side 
each tail page may have it's own LRU (why I don't know).

There is ofocourse much work to do in shm to make it hugepage aware, map 
pte(pde) etc.

At this stage I don't have BUGs and I can make 2MB shm area, read and delete 
it.
Signed-off-by: Radosław Smogura (mail@smogura.eu)
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Any suggestion are welcome.

If it's to early work I want to say sorry. I hope I fullfiled all code/submit 
conventions.

Regards,
Radosław Smogura



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