Plan B is to remove page->index.
- Replace ->mapping with a pointer to the page's radix tree
slot. Use address masking to go from page.radix_tree_slot
to the radix tree node.
- Store the base index in the radix tree node, use math to
derive page->index. Gives 64-bit index without increasing
the size of struct page. 4 bytes saved.
- Implement radix_tree_gang_lookup() as previously described. Use
this in truncate_inode_pages, invalidate_inode_pages, readahead
- The only thing we now need page.list for is tracking dirty pages.
Implement a 64-bit dirtiness bitmap in radix_tree_node, propagate
that up the radix tree so we can efficiently traverse dirty pages
in a mapping. This also allows writeback to always write in ascending
index order. Remove page->list. 8 bytes saved.
- Few pages use ->private for much. Hash for it. 4(ish) bytes
- Remove ->virtual, do page_address() via a hash. 4(ish) bytes saved.
- Remove the rmap chain (I just broke ptep_to_address() anyway). 4 bytes
saved. struct page is now 20 bytes.
There look. In five minutes I shrunk 24 bytes from the page
structure. Who said programming was hard?
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to email@example.com
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/